- Sherlock: "Shut up."
- Lestrade: "I didn't say anything."
- Sherlock: "You were thinking. It's annoying."
- — "A Study in Pink"
Detective Inspector Greg Lestrade is an inspector with New Scotland Yard. He often requires Sherlock Holmes' assistance to help with difficult cases. Greg has been affiliated with Sherlock for the better part of five years, but he still does not know everything about the consultant's antics and is therefore frequently surprised at his actions. 
Greg has respect for Sherlock and seems to possess none of the animosity his team has. He tries to get his team to cooperate with Sherlock whenever possible, even when Sherlock is being insulting. Despite this, he is often frustrated by Sherlock's cryptic deductions and lack of explanations for his conclusions, as well as his constant insults.
Greg first met Sherlock during a bizarre case, in which a body was found in a sauna; however, it turned out that the person in question had died of hypothermia.
Greg seems to like Dr John Watson and it takes a lot more time for him to warm up to Sherlock. Greg becomes closer to Sherlock and John after seeing their friendship strengthen, even attending a small Christmas party at 221B Baker Street.  He comes to Dartmoor where Sherlock and John are investigating sightings of a gigantic hound. He pretends to be there on holiday but Sherlock quickly deduces that he is there to help with the case; it is suggested but never confirmed that he was sent there by Mycroft Holmes. John tells Greg that Sherlock was secretly happy to see him, which pleases him somewhat. He later assists with the confrontation with Dr Bob Frankland in the Hollow. 
When Jim Moriarty claims he will kill anyone Sherlock cares about, Greg is one of the three people Moriarty has identified as a friend of Sherlock's and therefore is a target. Greg does everything he can to help Sherlock and ignores the doubts planted by Moriarty. Sally Donovan forces him to consider Sherlock's implication in the crime and to present the case to the Chief Superintendent. He later phones John to warn him of Sherlock's imminent arrest, an act that could have gotten him fired or even thrown in jail. 
- He is shown using nicotine patches in order to concentrate during cases, a trait he shares with Sherlock Holmes. Later, he is seen smoking regular cigarettes. While seeing this, Sherlock states "Those things'll kill you".
- After being estranged from his wife, he says that he is getting back with her; however Sherlock says that she is having an affair with a PE teacher (which surprises him).
- He splits up with his wife after this incident and is no longer wearing his wedding ring, a visible tan line evident on his finger.
- In the original stories, Lestrade's first name is never fully revealed; however, in "The Adventure of the Cardboard Box" it is said to begin with G. It is possible the series' use of Greg as his first name is a reference to Inspector Tobias Gregson, another recurring police inspector character from the original series with whom Lestrade is possibly a composite character, as Gregson tended to be rather less dismissive of Holmes' abilities than Lestrade.
- In the first episode, he says "Sherlock Holmes is a great man, and some day... he might even be a good one." In the Final Problem, this comes to pass when Sherlock, after years of friendship provided by John Watson, asks Lestrade to look after Mycroft while he's in shock. When one of his officers calls Sherlock a great man, Lestrade corrects him "No. He's a good one."
- Sherlock mistakes his first name as Gavin, Graham, Geoff or Giles, but finally calls him 'Greg,' much to Lestrade's surprise, in "The Final Problem." At the time, Sherlock had just been through a lot of trauma, likely making him appreciate his friends more and decide to show Lestrade respect by calling him by his first name.
- This running gag is possibly a reference to the fact that Lestrade didn't have a known first name in the Canon of Sherlock Holmes.
- ↑ 1.0 1.1 Moffat, Steven (writer) & McGuigan, Paul (director). (25 July, 2010). "A Study in Pink". Sherlock (2010). Series 1. Episode 1. BBC One.
- ↑ 2.0 2.1 Moffat, Steven (writer) & McGuigan, Paul (director). (1 January, 2012). "A Scandal in Belgravia". Sherlock (2010). Series 2. Episode 1. BBC One.
- ↑ 3.0 3.1 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.