Prior to turning professional, O'Brien played three seasons with the Acadie–Bathurst Titan of the Quebec Major Junior Hockey League (QMJHL).

In his final year, he recorded 176 points to help lead his team to the 2010 Telus Cup where he was then named the National Midget AAA Championship's MVP.

[7] On April 5, 2012, O'Brien signed an amateur tryout agreement with the St. John's IceCaps of the American Hockey League (AHL)[8] but he returned to the Acadie-Bathurst Titan for the 2012–13 season as an assistant captain after playing one game.

[16] After playing in 20 games for the Ravensburg Towerstars, O'Brien opted to conclude the season in North America with the ECHL's Wichita Thunder.

[17][18] After playing in 24 games for the Wichita Thunder and recording 19 points, O'Brien was loaned to the Binghamton Senators of the AHL on March 23, 2017.

[2] While playing for the Growlers, O'Brien scored the first hat trick in franchise history to help beat the Reading Royals 5–4 on November 16, 2018.

As a free agent, O'Brien returned to North America in the off-season, re-joining former club, the Toronto Marlies of the AHL, on a one-year contract on September 2, 2021.

[32] After spells with HC Slovan Bratislava and Newfoundland Growlers, O'Brien signed terms with the Cardiff Devils ahead of the 2024–25 season.