Adams was born in Toronto, Ontario, Canada. His father is journalist Claude Adams. He attended Northern Secondary School.
Following his parents' divorce, Adams moved from Toronto to Los Angeles at age 19, where he attended the University of Southern California, earning a B.F.A. After earning the Jack Nicholson Award in 2004, which provided scholarships directly funded by the eponymous actor to outstanding performers at the school and earning his BFA, he immediately began working on a production of Edward Albee's The Goat, or Who is Sylvia? at the Mark Taper Forum.
Adams appeared in episodes of Cold Case', 'Pretty Little Liars, Jack and Bobby, and has since had roles in Lost, Friday Night Lights, Without a Trace, Commander in Chief, Heartland, Ghost Whisperer, NCIS, Cupid, Luck, Raising the Bar Legends of Tomorrow, Lie To Me and Suits. He starred as twin brothers in the 2008 ABC pilot Good Behavior, executive produced by Rob Thomas.In 2009, he signed for the male lead in the one-hour drama The Dealership, starring opposite Tricia Helfer and William Devane. His television appearances grew over the next few years, from guest appearances on Numb3rs to a recurring role as a love interest for Adrianne Palicki on Friday Night Lights and leads in TV features like the romantic comedy Christmas in Boston.
In 2007, he moved up to guest appearances on top-rated shows like Lost, where he played a young man who sought out John Locke (played by Terry O'Quinn), while maintaining his presence in the Los Angeles theater scene, most notably with an award-winning production of "Marat/Sade," which he produced and directed for the Blue House Theatre Company.
In 2010, Adams guest starred in Pretty Little Liars, in the 5th episode; "Reality Bites Me" as Ezra Fitz's college friend, Hardy. In summer 2011, he began starring in the co-lead role of Mike Ross in Suits on the basic-cable USA Network, after being fired from the pilot of NBC's Friends With Benefits. He garnered much acclaim for his role in the series which has continued into its seventh season in 2017–18. Since Season 3, Adams has been listed as a co-producer of Suits (with co-star Gabriel Macht) and has directed some episodes. He appeared in HBO's 2012 TV series Luck as recurring character Nathan Israel.
In 2016, Adams was cast as Hourman in the TV show Legends of Tomorrow. He made an appearance in the end of Season 1 as Rex Tyler.
His work in film includes supporting roles in Old School and Two: Thirteen, and lead roles in Weather Girl (a 2009 Slamdance entry) and the 2009 Berlin International Film Festival competitor Rage, directed by Sally Potter.
Adams started dating Pretty Little Liars star Troian Bellisario after they met in 2009 when they were cast opposite each other in the play Equivocation. Prior to his appearance on Pretty Little Liars, Adams and Bellisario had broken up; but, after Adams' guest appearance on Pretty Little Liars in 2010, the two have since gotten back together. On February 24, 2014, it was confirmed that Bellisario and Adams had become engaged; on December 10, 2016, they married in California.
Adams endorsed Democratic Candidate Bernie Sanders in the run-up to the 2016 US Presidential Election.
Adams was awarded Honorary Life Membership of UCD Law Society in September 2013. Adams plays the guitar and is an avid photographer who owns over 25 cameras.