Career
He is currently playing with Timrå IK of the Swedish HockeyAllsvenskan. Mattsson played with Södertälje Saskatchewan in the Elitserien during the 2008-2009 Elitserien postseason. Mattsson was the last player selected in the 2011 National Hockey League Entry Draft, taken with the 211th overall pick by the Chicago Blackhawks in the 7th round.
Mattsson was later drafted by the Sudbury Wolves of the Ontario Hockey League with the 19th pick in the Canadian Hockey League Import Draft.
After attending training camp with the Blackhawks, Mattsson returned to the Wolves to start the 2011-2012 OHL season
In 2013 He joined the Swedish HockeyAllsvenskan (the division under the SHL) Djurgårdens IF Hockey as the new head goalkeeper, replacing Chet Pickard who went back to National Hockey League.