- "We solve crimes, I blog about it, and he forgets his pants."
- ―John Watson [src]
Dr. John Hamish Watson (MBBS) is the best friend and assistant of Sherlock Holmes and a former British Army doctor. Before marrying Mary Morstan, he lived at 221B Baker Street with Sherlock, a flat they rented from Mrs Hudson. He lived with Mary, whom he worked with before developing a romantic relationship.
John Watson has a sister, Harriet Watson (nicknamed 'Harry'), whom he does not see often. He was born in April, and is currently in his 40s.
John went to King Edward VI Grammar School in Chelmsford. He studied medicine at King's College (London), where he also did his Bachelor of Medicine and Surgery in 2004. John worked at the Broomfield Hospital Chelmsford and the University College Hospital London. He was trained at St. Bartholomew's Hospital as a British Army doctor and served as a Captain in the Fifth Northumberland Fusiliers. John was deployed to Afghanistan, where he served for three years until being shot in the shoulder. He recovered from the physical wound, but was left with psychological trauma – a psychosomatic limp and an intermittent tremor in his dominant hand. The limp was bad enough to require a cane to help him walk, and shortly thereafter he was discharged from service.
John was seeing a therapist for post-traumatic stress, but did not make much progress. As part of his treatment, he was instructed to keep a blog to record his day-to-day life, thoughts, and feelings as he adjusted to civilian life after leaving the army. However, he failed to keep up with it, claiming that "nothing happens to [him]". 
John is introduced to Sherlock Holmes via an old friend from St. Bartholomew's Hospital, Mike Stamford. Mike is now an instructor at the hospital and, upon hearing John needs a new place to live, mentions another person saying the same thing that morning. Mike takes John to a lab in the morgue to introduce him. Within seconds and with a few fleeting glances, Sherlock has deduced key elements of John's life, and although both awestruck and off-put, John agrees to meet Sherlock the next day at 221B Baker Street.
Upon seeing the flat, John expresses interest in renting it. He also learns that Sherlock is a consultant for Greg Lestrade of Scotland Yard. Sherlock requests he come along to a crime scene as his assistant. There, John witnesses more of Sherlock's uncanny deductive ability as well as his complete animosity toward the Yard's investigative team. Sally Donovan goes so far as to warn John to stay away from Sherlock.
Sobered by this information and abandoned by Sherlock at the crime scene, John returns to a main road to pick up a cab. Instead, he is intercepted by a strange car and taken to a secure location to have a talk with Sherlock's brother, Mycroft Holmes. Mycroft never introduces himself, and due to his questionable attitude and methods, John is unwilling to take what he has to say seriously. Mycroft offers him money to spy on Sherlock, which John declines. "You're very loyal very quickly," Mycroft observes. He also notes that John's therapist has reported that he has a tremor in his left hand. However, upon observing the same hand during their conversation, Mycroft says, "You're under stress right now and your hand is perfectly steady. You're not haunted by the war, Dr Watson. You miss it."
Despite several warnings to the contrary, John returns to 221B – first stopping off at his old residence to collect his firearm – and continues to aid Sherlock in the murder investigation. This leads them to pursuing a cab through London on foot, a course of action that is ultimately fruitless, but helps Sherlock prove a point. When faced with the apprehension of a potential suspect, John forgets entirely about his psychosomatic limp and is able to keep up with Sherlock during the chase. When they return to Baker Street, Sherlock tells the landlady, Mrs Hudson, that John will indeed be renting the flat.
John comes to Sherlock's rescue after Sherlock goes off on his own to confront a serial killer. John uses a victim's mobile phone, left in the possession of the killer, to track their location via GPS. He shoots the killer from an adjacent building, thinking that Sherlock's life is in danger. He is an excellent marksman, able to shoot through two windows and over Sherlock's shoulder in order to fatally wound the suspect. Afterward, John moves into 221B and begins blogging about their adventures. 
Despite Sherlock's consultant status and John's army pension, money remains tight, prompting John to seek employment at a medical centre. There he meets another doctor, Sarah Sawyer, with whom he is attempts to begin a relationship. He sets out to aid Sherlock with a new case, an endeavour that cuts into his work day. Sarah covers for him when he falls asleep on the job and John manages to get a date out of her. He unwisely accepts Sherlock's recommendation of a place to take her, and all three of them end up at a visiting Chinese circus while Sherlock investigates the performers as part of their case. John and Sarah are later abducted by members of the Black Lotus Tong, mistakenly thinking John is Sherlock. Sherlock appears to set the record straight and save the two. 
Later, it is revealed that John has been blogging about specific cases of Sherlock's, and it is gaining some popularity – particularly with the members of Scotland Yard. Their next case is unlike any they have seen before. An anonymous bomber is deliberately playing a game of wits with Sherlock. John assists as best he can, but their adversary is intent upon blowing up his victims if Sherlock cannot solve certain cases within a specific amount of time. John becomes concerned for the innocent lives hanging in the balance between Sherlock and their mysterious bomber, and equally concerned that Sherlock does not seem to care about human life at all. An argument ensues between the two, and John is angered by Sherlock's cold attitude, but relents to continue aiding in the investigation.
John is later abducted by the bomber – revealed to be Jim Moriarty – and used as the final victim in a confrontation with Sherlock. John attempts to sacrifice himself, attacking Moriarty, so that if the bomb were to detonate, he would take Moriarty out with him. Moriarty sees that John values Sherlock's life above his own and in turn has his snipers train their weapons on Sherlock. This forces John to back off from Moriarty. Sherlock removes the explosives from John's coat. The two then decide it would be worth both their deaths to detonate the bomb and take Moriarty out with them. The high-tension standoff is interrupted when Moriarty's mobile phone rings.  Whatever the caller has to tell him is enough to make him call off his snipers and allow Sherlock and John to live another day.
Several months pass, during which the pair investigate other cases and John blogs about them. His blog becomes popular with the general public, which forces them to avoid attention from the media. Still, John is pleased with the development, telling an annoyed Sherlock that the blog is helping him make a living. During this time, John ends his relationship with Sarah and enters the dating pool again, with limited success.
The two are summoned to Buckingham Palace by Mycroft to investigate a matter of delicate importance to the British Royal family. A young female person in close relation to the Queen has had compromising photographs taken of her while in the company of Irene Adler, a dominatrix known professionally as 'The Woman'. They are being employed to get the photos back before Irene can use them as blackmail. Irene proves to be an intellectual match for Sherlock and escapes their grasp. John has his own inklings about Sherlock's feelings toward Irene.
When Irene turns up dead that Christmas, Sherlock is upset by the news to an unprecedented extent. John is baffled and concerned by the behaviour, wondering if Sherlock is capable of being heartbroken. Then, Irene contacts John, revealing that she had faked her death to escape her enemies. John's stance is for her to tell Sherlock she is alive. She wants his help, but John holds Sherlock's well-being in higher regard than anything she has to offer him.
John is still no closer to understanding Sherlock's capacity for emotion, yet he still he opts not to tell Sherlock that Irene Adler wound up dead after all, instead following Mycroft's suggestion to tell Sherlock she was put in a witness protection scheme in America. He also breaks police protocol and allows Sherlock to keep Irene's mobile phone as a memento. John remains unaware that Irene is actually alive, and at the last moment whilst she was to be executed in another country, Sherlock came to her rescue. 
Sherlock and John end up infiltrating Baskerville Military Base, a top secret government base after being called to investigate the specifics of a case. John expresses skepticism about clearing security with an ID stolen from Mycroft, but then pulls rank on a young army officer to aid Sherlock's cover story. Sherlock is impressed by John's ability to think on his feet.
The case brings out John's instincts as a doctor. Their client, Henry Knight, is in a state of visible emotional trauma, which John attempts to treat with bed rest and a prescription. Additionally, when Sherlock finds himself on unsteady mental ground, John keeps his cool. He attempts to steer Sherlock back to thinking rationally, citing mental stress and overwork as a reason why Sherlock might have thought he saw a demon hound out on the moor with Henry Knight. Sherlock's difficult behavior ultimately angers him, but not so much that he will not interview Henry's therapist, Dr Louise Mortimer, as a favor to Sherlock. When speaking with Mortimer, John expresses concern for Sherlock's well-being despite the argument that they had.
John inspires Sherlock to recognise the clue that solves the case: the use of acronyms to abbreviate the name of a government project. John mistakenly applies the idea to something irrelevant, but Sherlock then realises the clue of the word "hound" should actually be "H.O.U.N.D." They then uncover traces of a defunct experiment, with that code name. 
John's blog has inspired more widespread media coverage of Sherlock, and Sherlock has been solving increasingly high-profile cases as a result. John sticks with him, making sure he can conduct himself cordially in public. John is worried about the repercussions of Sherlock's newfound fame and warns him that the press will turn on him.
Before long, Jim Moriarty resurfaces in highly dramatic fashion and begins systematically destroying Sherlock's reputation and credibility. During this time, Mycroft summons John to the Diogenes Club to warn him that Moriarty has stationed four assassins around 221B Baker Street, although their motives are currently unknown.
Moriarty sets up a crime and plants enough evidence that it appears Sherlock committed it himself. With Scotland Yard wanting to arrest him, Sherlock asks John if he has doubts as well as to whether Sherlock could be a fraud. John remains steadfast and loyal, although he adds, "I know you're for real. No one could fake being such an annoying dick all the time".
When the Yard does arrest Sherlock, John is outraged. He punches a high-ranking officer, ensuring that he will be arrested as well. Sherlock "implements a daring escape" and they flee together as fugitives. Trying desperately to find a solution, they find themselves in the flat of journalist Kitty Riley, who claims she will be soon publishing an exposé on Sherlock's life. Her source is a man claiming to be Richard Brook, an actor Sherlock hired to play the part of his nemesis. It is really Moriarty, and he appears to them at that point. John loses his temper, vehemently refusing to believe the lies Moriarty has spun. Sherlock remains silent while John vouches for his character.
Moriarty escapes again, and the two split up to investigate separate avenues. John returns to Mycroft, having realised Kitty's story contains so much factual evidence about Sherlock that someone must have tipped off Moriarty to it. Mycroft confesses that the government had Moriarty detained and interrogated, but he would only cooperate if Mycroft told him about Sherlock's life. Moriarty was then released. John leaves in disgust.
Sherlock is hiding out in the Barts morgue, where John joins him. Then John receives a phone call that Mrs Hudson has been shot. John wants to return to her immediately, but Sherlock coldly tells him he needs to stay where he is. In a fit of emotion, John insults Sherlock and leaves. When he arrives back at 221B, he discovers Mrs Hudson is fine, and he was only given the call to get him away from Barts. He rushes back to the scene just in time to get a suicide phone call from Sherlock, who is standing on the top of the building. Sherlock tries to convince John that he is indeed a fraud, but John, although confused and scared, still refuses to believe it. Sherlock then jumps from the roof, and John is unable to get to him until it is too late.
From that point on, John believes Sherlock is dead, although when visiting his grave, he expresses hope that somehow Sherlock will be able to cheat death and return. Despite having stopped the therapy sessions, eighteen months after meeting Sherlock, John schedules another due to the death of his friend. 
However, John is able to move on from Sherlock's death, and begins dating Mary Morstan. As he was about to propose to her, he realises that the waiter was in fact Sherlock in disguise. After almost having a panic attack, he manages to calm down enough to lunge at Sherlock, and the two fight in the restaurant. They move to a small take-away shop, where Sherlock explains everything, however John is still upset. He leaves shortly after with Mary, although she assures Sherlock that she will talk to John. Later, John is drugged and kidnapped by two men. When he regains consciousness, he is inside a bonfire to be lit during a Guy Fawkes Night celebration. Mary receives a series of texts which contain clues and enable her and Sherlock to rescue John seconds after the flames are ignited and John is nearly burned alive He ends up reconciling with Sherlock, and after finally managing to propose to Mary, asks him to be best man.
Over the months between learning Sherlock is alive and his wedding, John helps Sherlock with a number of cases, and the two fall back into their former friendship. Sherlock's 'Best Man' speech references these cases, and he is able to prevent one of John's wedding guests from being murdered as he re-examines the cases while talking about them. John finds out at the end of the reception that Mary is pregnant and he is going to be a father. 
However, their relationship hits a rocky patch when, while investigating a businessman by the name of Charles Augustus Magnussen, he learns that Mary is a former CIA-agent. She shoots Sherlock, however he tricks her into coming clean in front of John. He is unable to deal with it and so distances himself from her, referring to her not as his wife, but a client. Christmas Day that year, Sherlock invites John and a heavily pregnant Mary to Christmas lunch at his parents house, where the two make up.
John is extremely brave, resourceful and practical. He is extremely loyal to Sherlock, and will usually, but not always, do what Sherlock asks him to, and cares a great deal about his well-being. Sherlock likewise cares about John. He is also very selfless and modest, as he puts himself at colossal personal risks to help Sherlock Holmes and is rather sceptical about his companion's ideals. He is very sarcastic and has an erratic sense of humour.
John deals with lack of stimulation little better than Sherlock does, the difference being that when Sherlock is bored he is very vocal in his frustration; when John feels that "nothing ever happens", he withdraws into a shell and shows strong tendencies towards depression (possibly exacerbated by his post-traumatic issues). He is adept at reading people through facial expressions, whilst Sherlock relies on his surroundings, on clothing and personality displays to read people.
- Expert Physician: According to his CV, John is "able to recognize and give immediate and appropriate treatment to a wide range" of illnesses and dysfunctions, including "myocardial infarction, acute coronary syndrome, pulmonary embolus and Sickle Cell Crisis, deep vein thrombosis, acute asthma attack, severe exacerbation of chronic obstructive pulmonary disease, diabetic keto-acidosis, community and hospital acquired pneumonia, seizures, poisoning/overdose, acute abdomen and post-operative oliguria hypotension".
- Expert Marksman: Due to his military career, John is incredibly proficient with firearms, far more so than Sherlock or Lestrade, proving to be able to judge the distance and split-second timing of a shot across a large area with two windows in the way, and fatally wound his target while missing Sherlock, who was standing very close to the target.
- Expert Combatant: His military career has also given John skill in unarmed combat. His skill in unarmed combat is also displayed where he sprains someone's arm in a single move and, as he is a medical expert, he is perfectly aware that he sprained it and how bad it should be.
Mike Stamford and John were, according to John, "sort of mates" when they were students.
There have been several women John has expressed an interest in:
- Sarah Sawyer
- "the one with the nose" (girlfriend)
- "the one with the spots" (girlfriend)
- Jeanette (girlfriend)
- Dr Louise Mortimer
- Mary Watson (wife)
John is also fond of Mrs Hudson. Both Sherlock and John become angry at Mycroft for telling Mrs Hudson to shut up, and John fusses over her after she had been attacked by CIA agents. Since neither of the two men are on good terms with their relatives, they may form a sort of surrogate family between them.
People assumed several times that John is homosexual and in a relationship with Sherlock. However, whenever people say this John makes a point of correcting them, in noticeable contrast to Sherlock, who never responds.
- "I always hear 'punch me in the face' when you're speaking but it's usually sub-text."
- ―John to Sherlock [src]
- "Listen, what I said before, John, I meant it. I don't have friends. I've just got one."
- ―Sherlock to John. [src]
- He played the clarinet when he was at school.
- He has had multiple girlfriends, whose relationships with him do not seem to last long.
- He played rugby at the Blackheath Rugby team.
- Thompson, Steve (writer) & Lyn, Euros (director). (1 August, 2010). "The Blind Banker". Sherlock (2010). Series 1. Episode 2. BBC One.
- Moffat, Steven (writer) & McGuigan, Paul (director). (25 July, 2010). "A Study in Pink". Sherlock (2010). Series 1. Episode 1. BBC One.
- Gatiss, Mark (writer) & McGuigan, Paul (director). (8 August, 2010). "The Great Game". Sherlock (2010). Series 1. Episode 3. BBC One.
- Moffat, Steven (writer) & McGuigan, Paul (director). (1 January, 2012). "A Scandal in Belgravia". Sherlock (2010). Series 2. Episode 1. BBC One.
- Gatiss, Mark (writer) & McGuigan, Paul (director). (8 January, 2012). "The Hounds of Baskerville". Sherlock (2010). Series 2. Episode 2. BBC One.
- Thompson, Steve (writer) & Haynes, Toby (director). (15 January, 2012). "The Reichenbach Fall". Sherlock (2010). Series 2. Episode 3. BBC One.
- Gatiss, Mark (writer) & Lovering, Jeremy (director). (1 January, 2014). "The Empty Hearse". Sherlock (2010). Series 3. Episode 1. BBC One.
- Thompson, Steve; Moffat, Steven; Gatiss, Mark (writers) & McCarthy, Colm (director). (5 January, 2014). "The Sign of Three". Sherlock (2010). Series 3. Episode 2. BBC One.
- Moffat, Steven (writer) & Hurran, Nick (director). (12 January, 2014). "His Last Vow". Sherlock (2010). Series 3. Episode 3. BBC One.
|Sherlock Holmes (Benedict Cumberbatch) • John Watson (Martin Freeman) • Mycroft Holmes (Mark Gatiss) • Jim Moriarty (Andrew Scott) • Greg Lestrade (Rupert Graves) • Molly Hooper (Louise Brealey) • Mrs Hudson (Una Stubbs)|
|Irene Adler • Mary Watson • Charles Augustus Magnussen • Eurus Holmes|
|"A Study in Pink" • "The Blind Banker" • "The Great Game"|
|"A Scandal in Belgravia" • "The Hounds of Baskerville" • "The Reichenbach Fall"|
|"The Empty Hearse" • "The Sign of Three" • "His Last Vow"|
|"The Six Thatchers" • "The Lying Detective" • "The Final Problem"|
|Unaired Pilot • "Many Happy Returns" • "The Abominable Bride"|
|"Sherlock: The Network" • Manga|