Fresh off being named the most improved player for Vancouver of the Western Hockey League in 2004-05, Franson was selected by the Nashville Predators in the third round (No. 79) of the 2005 NHL Draft.

The following season, Franson tied for third among WHL defensemen with 55 points and helped Vancouver win the league title. He tied for the lead among WHL defensemen with 20 points in 18 playoff games, then topped everyone at his position with five points during the Memorial Cup.

In 2006-07, Franson was named to the All-Tournament Team as Vancouver won the Memorial Cup. He also won a gold medal with Canada at the World Junior Championship.

With Milwaukee of the American Hockey League in 2007-08, Franson led rookie defensemen with 11 goals, 23 assists and 34 points and was named to the AHL All-Rookie Team.

Franson made his NHL debut with the Predators on Oct. 17, 2009, against the Washington Capitals. He got his first career NHL point with an assist Oct. 21, 2009, against the Boston Bruins and the next night scored his first NHL goal, against the Ottawa Senators. With 21 points in 61 games in 2009-10, Franson became second rookie defenseman in Predators history to reach the 20-point mark, joining Dan Hamhuis (2003-04). He led NHL rookies with a plus-15 rating.

Franson had 29 points in 2010-11 and then had four assists for the Predators in their Stanley Cup Playoff first-round series against Anaheim. Traded to the Toronto Maple Leafs with Matthew Lombardi for Brett Lebda, Robert Slaney and a 2013 fourth-round draft pick on July 3, 2011, Franson had a four-game point streak for Toronto from Dec. 5-13, 2011.
He ranked fourth among NHL defensemen in assists (25) and tied for sixth in points (29) in 2012-13, and had six points in seven playoff games. In 2013-14, Franson ranked second in the NHL in hits (282).

Franson had a nine-game point streak from Nov. 4-20, 2014. He was traded by Toronto to Nashville with Mike Santorelli in exchange for Olli Jokinen, Brendan Leipsic and a first-round pick in the 2015 NHL Draft on Feb. 15, 2015.

Franson signed a two-year contract as a free agent with the Buffalo Sabres on Sept. 10, 2015.

NOTES & TRANSACTIONS

• WHL West Second All-Star Team (2006)
• WHL West First All-Star Team (2007)
• AHL All-Rookie Team (2008)
• AHL Second All-Star Team (2009)
• AHL Central Division All-Star Team (2021)
• Traded to Toronto by Nashville with Matthew Lombardi for Robert Slaney, Brett Lebda and Toronto's 4th round pick (later traded to St. Louis -- St. Louis selected Zachary Pochiro) in 2013 NHL Draft, July 3, 2011.
• Signed as a free agent by Gavle (Sweden), October 1, 2012.
• Traded to Nashville by Toronto with Mike Santorelli for Olli Jokinen, Brendan Leipsic and Nashville's 1st round pick (later traded to Philadelphia -- Philadelphia selected Travis Konecny) in 2015 NHL Draft, February 15, 2015.
• Signed as a free agent by Buffalo, September 11, 2015.
• Signed as a free agent by Chicago, October 4, 2017.