Gallagher was born in New Westminster, British Columbia, Canada, and grew up in Chilliwack, British Columbia. Born to an Irish American father and a Chinese mother, Gallagher holds dual American and Canadian citizenship.
Gallagher is known for his television roles as Joe Finn in Da Vinci's Inquest, the alcohol salesman in Entourage, Leon in The Line, Farhod the Fierce in Pair of Kings, and Ken Tanaka in Glee, and his film roles as Awkward Davies in Master and Commander: The Far Side of the World and Gary the bartender in Sideways. He played Attila the Hun in Night at the Museum and its sequels, Chow in True Blood, Colquitt in Final Destination 3, Anderson in Severed: Forest of the Dead, and the head of security, Hugo, in the short-lived series Endgame. Gallagher made guest appearances in Battlestar Galactica, Smallville, Hawaii Five-0, Intelligence, NCIS: Los Angeles, Fuller House and Psych in addition to Hell's Kitchen as a guest for the 100th dinner service. He landed the recurring role of a prison guard on the ABC soap opera General Hospital. He voiced Khotun Khan in Ghost of Tsushima.
|1996||Moving Target||Jonish Kukoc|||
|1999||Apocalypse II: Revelation||Jake Goss|
|2001||Apocalypse IV: Judgment||Jake Goss|
|2001||Full Disclosure||Larry Quinn|
|2003||Master and Commander: The Far Side of the World||Awkward Davies, Able Seaman|
|2004||Sideways||Gary, The Bartender|
|2006||Night at the Museum||Attila The Leading Hun|
|2008||Street Kings||LAPD Captain|
|2009||Night at the Museum: Battle of the Smithsonian||Attila The Leading Hun|
|2014||Night at the Museum: Secret of the Tomb||Attila The Leading Hun|
|2017||Downsizing||Drunk Guy At The Bar|
|2019||A Dog's Way Home||Teo|
|2019||Captain Marvel||Security Chief|
|2020||The Christmas Chronicles 2||Mass State Police Troop|
|1994||RoboCop: The Series||Security Guard||Episode: "The Future of Law Enforcement: Part 1" (S 1:Ep 1 – Pilot)|
|1994||Kung Fu: The Legend Continues||Bodyguard||Episode: "Tournament" (S 2:Ep 9)|
|1995||Forever Knight||Michael||Episode: "Sons of Belial" (S 3: Ep 11)|
|1997||Bad to the Bone||Trucker||Made-for-TV Movie directed by Bill L. Norton|||
|1997||Earth: Final Conflict||Prison Guard||Episode: "Avatar" (S 1:Ep 4)|
|1997||F/X: The Series||Macho||Episode: "Spanish Harlem" (S 2:Ep 9)|
|1998||My Date with the President's Daughter||Secret Service Agent||Part of The Wonderful World of Disney|||
|2006||Stargate Atlantis||Vonos||Episode: "Inferno"|
|2007||Masters of Horror||Barman||Episode: "The Black Cat"|
|2008–2009||True Blood||Lin Chow||2 episodes|
|2009–2010||Glee||Ken Tanaka||Season 1
|2010||Hawaii Five-0||Carlos Bagoyo||Episode: "Nalowale"|
|2010||Entourage||Randy||Episode: "Tequila and Coke"|
|2011||Suits||Joe, The Security Guard||Episode:"The Shelf Life"|
|2011||Endgame||Hugo, Head of Hotel Security||Season 1|
|2012||Psych||Mercer||Episode: "True Grits"|
|2013||Almost Human||Tony Han||Episode: "The Bonds"|
|2015–2017||iZombie||Jeremy Chu||Seasons 2–3|
|2016||Fuller House||Chief Mulrooney||Episode: "Secrets, Lies and Firetrucks"|
|2013||Unclaimed||Jeff Keeley||Television film|
|2017–present||General Hospital||Prison Guard||Recurring|||
|2018||Lucifer||Barry||Episode: "Orange Is the New Maze"|
|2018||Dirty John||Detective Dave Nissely||Episode: "One Shoe"|
|2018–2019||Siren||Dr. Abbott||4 episodes|
|2019||Wayne||Mr. Hernandez||2 episodes|
|2019||Project Blue Book||Randal Kavanaugh||Episode: "Foo Fighters"|
|2019||The Twilight Zone||Jack Mongoyak||Episode: "A Traveler"|
|2019||American Princess||Friar Woodruff||5 episodes|
|2019||Creeped Out||Coach Carter||Episode: "The Takedown"|
|2020||Fortunate Son||William Sullivan||8 episodes|
|2020||Station 19||Keller||Episode: "I'll Be Seeing You"|
|2020–present||Big Sky||Sherriff Tubb||Recurring cast|
|2006||Company of Heroes||Unknown|
|2009||Night at the Museum: Battle of the Smithsonian||Attila The Hun|
|2010||Halo: Reach||Trooper 3|
|2018||Red Dead Redemption 2||The Local Pedestrian Population|
|2019||Tom Clancy's Ghost Recon Breakpoint||Mads Shultz|
|2020||Ghost of Tsushima||Khotun Khan|||
- "B.C. actor Patrick Gallagher explores his dual nature with Glee". The Vancouver Sun. Vancouver, British Columbia: Postmedia Network Inc. PressReader. November 24, 2009. Retrieved November 24, 2009.
- Balser, Erin; Gardner, Suzanne (2010). Don't Stop Believin': The Unofficial Guide to Glee. Toronto: ECW Press. ISBN 978-1550229387.
- Soaps.com (September 11, 2017). "GENERAL HOSPITAL COMINGS & GOINGS". Soaps.com. United States: SheKnows Media. Retrieved September 17, 2017.
- "Moving Target". Turner Classic Movies. Atlanta: Turner Broadcasting System (Time Warner). Retrieved September 17, 2017.
- "Pale Saints". Turner Classic Movies. Atlanta: Turner Broadcasting System (Time Warner). Retrieved September 17, 2017.
- "Bad to the Bone". Turner Classic Movies. Atlanta: Turner Broadcasting System (Time Warner). Retrieved September 17, 2017.
- "My Date with the President's Daughter". Turner Classic Movies. Atlanta: Turner Broadcasting System (Time Warner). Retrieved September 17, 2017.
- "Behind The Voice Actors - Patrick Gallagher". Behind The Voice Actors. Retrieved December 1, 2020.