Nevertheless, the Vancouver Giants in the Western Hockey League (WHL) offered him a tryout and Franson was successful in making the team.

In the 2007–08 season, Franson turned professional and was assigned to the Predators' American Hockey League (AHL) affiliate, the Milwaukee Admirals.

On July 3, 2011, Franson, along with forward Matthew Lombardi, was traded to the Toronto Maple Leafs in exchange for Brett Lebda and Robert Slaney.

[7] During the subsequent 2011–12 season, Franson played 57 games for the Maple Leafs, scoring 21 points and finishing with a plus-minus rating of –1.

On February 15, 2015, Franson was traded back to the Predators, along with Mike Santorelli, in exchange for Olli Jokinen, Brendan Leipsic and a first-round draft pick.

[10] Over his two seasons with the Sabres, entrenched in a top four role, Franson appeared in 127 games for 36 points but was unable to help the rebuilding club make the post-season.

In the 2018 Calder Cup Playoffs, Franson helped the IceHogs reach the Western Conference Finals for the first time in team history, collecting 13 points in 13 games and finished second among AHL defensemen in the postseason.

As a free agent from his stint in Russia, and with the ongoing COVID-19 pandemic, Franson opted to return to North America, agreeing to a one-year AHL contract with his former club, the Rockford IceHogs, on September 23, 2020.

On July 22, 2021, Franson left the IceHogs as a free agent and continued playing in the AHL, agreeing to a one-year contract with the Hershey Bears, the primary affiliate of the Washington Capitals.