The defenseman was loaned to ZSC Lions by the Chicago Blackhawks in January, and will head back to National League A after the team announced the signing Friday.
Neue Zürcher Zeitung and Chris Johnston of Sportsnet were the first to report the deal being in place.
Rundblad and the Blackhawks mutually agreed to terminate his contract in late July. He was set to earn $1.1 million in 2016-17, Runblad won't account for any money against the Hawks' salary cap this coming season.
The 25-year-old played nine games with two assists for Chicago last season.