Baruchel got his first acting job when he was just 12. One of his first major acting roles was on local television series My Hometown in 1996. From 1997 to 1998, he co-hosted Popular Mechanics for Kids with Elisha Cuthbert. After appearing briefly in Cameron Crowe’s Oscar winning film Almost Famous, Baruchel won the role of Steven Karp on Judd Apatow’s acclaimed yet short-lived television series Undeclared, where he starred alongside Seth Rogen, Carla Gallo, Charlie Hunnam and Monica Keena. He then appeared with James Van Der Beek in Roger Avary’s The Rules of Attraction.

In 2004, Baruchel played boxing hopeful Danger Barch in Clint Eastwood’s Million Dollar Baby. Baruchel then starred in Nemesis Game and Fetching Cody, before appearing opposite Don Johnson on the WB’s Just Legal in 2005, and guest-starring on the CBS drama Numb3rs in 2006.

Baruchel appeared in the films Knocked Up (which reunited him with Judd Apatow, Jason Segel, and Seth Rogen), I’m Reed Fish, Just Buried, and the Ben Stiller-directed Tropic Thunder, alongside Jack Black, Nick Nolte, Steve Coogan and Robert Downey Jr. He co-starred with Seth Rogen in the 2007 trailer for Jay and Seth versus the Apocalypse, created by Rogen and Evan Goldberg as a strategy to garner interest and funding for a similar, larger-scale project (later made in 2013 as This Is the End). In 2008, he appeared in Nick and Norah’s Infinite Playlist. He also made a brief appearance in Night at the Museum 2: Battle of the Smithsonian.

In 2010, Baruchel starred in the films The Trotsky, DreamWorks’ She’s Out of My League (opposite Alice Eve), and the live-action Disney adaptation of The Sorcerer’s Apprentice. He also voiced the starring role in the acclaimed animated feature, How to Train Your Dragon, a role he has subsequently continued throughout the franchise, including its television series. Also in 2010, he played two supporting characters in the Canadian comedy series The Drunk and On Drugs Happy Fun Time Hour. He developed the screenplay for Goon, with Evan Goldberg, playing Johnny Klutz, a character of his own creation. Goon co-stars Seann William Scott and fellow Canadian actor Eugene Levy.

Baruchel also appeared in the 2010 Adidas Originals ad campaign, “Cantina”, in conjunction with the FIFA World Cup and in video clips for Canadian prog-rockers Rush’s 2012–13 Clockwork Angels tour.

In July 2012, he appeared in the music video for the song “Toxsik Waltz” by rapper Necro. In the summer of 2013, he starred in the hit apocalyptic comedy This Is the End and in 2014, he appeared in the RoboCop remake and reprised his role as Hiccup in How to Train Your Dragon 2.

Baruchel was engaged to actress Alison Pill from 2011 to 2013. He alluded to their break-up in a Twitter post on February 16, 2013. In May 2018, Baruchel announced his engagement to his girlfriend Rebecca-Jo Dunham. They were married on September 21, 2019 in Portugal. Baruchel has said that he is “probably agnostic”.

In July 2014, it was announced that Baruchel would be starring in the FXX comedy Man Seeking Woman which premiered in January 2015. He also appeared in the 2015 music video for the song “Every Little Means Trust” by Idlewild.

Baruchel wrote, directed and starred in the 2017 sports comedy film Goon: Last of the Enforcers, the sequel to the 2011 film Goon.

In 2018, he made his debut as an author, with Born Into It: A Fan’s Life, released on Harper Collins. The book explored his love of the Montreal Canadiens with anecdotes, childhood memories and heartfelt tales about his life as a fan of the team.