Undrafted, Conacher played for the Tampa Bay Lightning, Ottawa Senators, Buffalo Sabres, and the New York Islanders of the National Hockey League (NHL).

He was subsequently signed after his senior year in 2010–11 to amateur try-out contracts with the Rochester Americans, Cincinnati Cyclones and the Milwaukee Admirals.

[2] In the 2011–12 season, after attending the Tampa Bay Lightning pre-season camp,[3] Conacher was selected to play in the 2012 AHL All-Star Classic, after leading all rookies in scoring.

[4] Upon helping the Admirals capture their first Calder Cup, Conacher's successful season was rewarded with the Les Cunningham Award as the league's MVP, becoming just the fourth rookie to win it since it was first presented in 1948.

Conacher continued to be productive and placed second in NHL rookie scoring with 24 points in 35 games before being dealt at the trade deadline (along with a 2013 fourth-round draft pick) to the Ottawa Senators in exchange for goaltender Ben Bishop on April 3, 2013.

Conacher's offensive struggles were perhaps magnified by the fact that goaltender Bishop, the player he had been traded for, was playing very well in Tampa Bay and was frequently receiving mention as a Vezina Trophy candidate.

He cleared waivers and was assigned to the team's minor league affiliate, Bridgeport Sound Tigers, the following day.

[12] He was assigned to AHL affiliate, the Utica Comets, securing an offensive role to help the club reach the Calder Cup finals.

On July 1, 2015, Conacher left the NHL as a free agent and signed a two-year contract with Swiss club, SC Bern, of the NLA.

On July 13, 2016, Conacher once again signed with the Tampa Bay Lightning of the National Hockey League to a one-year, one-way contract.

[25] He was later signed to a professional tryout contract to attend the Carolina Hurricanes training camp in preparation for the 2023–24 season on August 29, 2023.

When he was ten days old he underwent a ten-hour surgical procedure in which doctors reconstructed his pelvis in order to place his bladder back into his body.