Flanagan played college hockey with the St. Lawrence Saints in the NCAA Men's Division IECAC Hockey conference. In his senior year, Flanagan's outstanding play was rewarded with a selection to the 2012–13 ECAC All-Conference First Team.[1] He signed a one-year entry-level contract with the Philadelphia Flyers on March 21, 2013.[2]
On August 1, 2014, Flanagan signed his first European contract as a free agent in agreeing to a one-year deal with Modo Hockey of the Swedish Hockey League.[3] In his tenure abroad, Flanagan featured in 38 games with Modo, registering 4 goals and 15 points as the club missed the post-season and narrowly avoided relegation in the 2014–15 season.
On September 22, 2015, Flanagan accepted an invitation to the Stockton Heat training camp,[4] and was later signed by ECHL affiliate, making a professional return to Adirondack with the Thunder.[5] After appearing in 44 games with the Binghamton Senators, Flanagan signed a two-year AHL contract on July 26, 2016.[6]
After completing his contract with the Belleville Senators following the 2017–18 season, Flanagan opted to end his 6-year professional playing career, announcing his retirement on August 22, 2018.[7]