|Season(s)||1, 2, 3, 4, 5|
|Portrayed by||Aidan Quinn|
|Occupation||Captain of the New York City Police Department 11th Precinct|
|Children||Hannah Gregson, Several unnamed daughters|
|Other relatives||Unnamed mother-in-law|
Thomas "Tommy" Gregson is a NYPD Captain of the 11th precinct. He previously worked at Scotland Yard which is where he met Sherlock Holmes.
Tommy Gregson started working for the NYPD thirty years ago. He was assigned to Scotland Yard a few months after the September 11 attacks to observe their counter-terrorism bureau. Although Sherlock was mostly assigned to homicides, their paths still crossed a few times. Ten years later, When Sherlock moves to New York City where Tommy currently lives and works as Captain of the New York Police Department, he hires him as a consultant detective.
He is married to Cheryl Gregson, and has several adult daughters. One of them is named Hannah and she works as a police officer at the same precinct as her father and wishes to become a captain like him (Rip Off).
When Sherlock is kidnapped, Joan becomes worried when he doesn't answer her messages. Suspecting that he may have relapsed, she tells Tommy that she's a sober companion for recovering drug addicts, and that Sherlock is her client. After Sherlock is found, Tommy tells him that he knew he was in rehabilitation before he hired him to work for the NYPD, and that since his services as a consulting detective hasn't altered, he doesn't see a problem with it.
It is revealed after a break-in in his house that he and his wife are on a trial separation. Cheryl is tired of Tommy's job being prioritized over her, but Tommy thinks the trial separation is just a break for Cheryl and that she'll come back. After realizing why his wife wanted a separation, he lets her know that she deserves better and that he is going to use the separation to figure out how to give it to her. Does Tommy dye his hair in the first few episodes of season 2 but then not in the later episodes?
Arthur Conan Doyle's Inspector Gregson on Wikipedia, which Elementary's Tommy Gregson is based on.