German Rupp has agreed a two-and-a-half year contract with the Premier League strugglers as manager Daniel Farke returned to the Bundesliga for his side's second signing of the January transfer window.
The 29-year-old has played nine seasons in the German top-flight for a host of clubs including Borussia Monchengladbach, Paderborn, Stuttgart and Hoffenheim.
Rupp, who has made seven league appearances for Hoffenheim this season, told Norwich's website: "I was in the training camp in Marbella with Hoffenheim and then two days later I'm here, so it's been very quick. But I'm very happy to be here.
"It's a childhood dream. I was in the Bundesliga for 10 years now and it's a new chapter for me. I wanted to be part of the team here and help the team stay in the Premier League."
Rupp's arrival at Carrow Road follows German coach Farke moving to sign Hertha Berlin midfielder Ondrej Duda on loan last week.
The Canaries lie bottom of the table, eight points from safety, after Saturday's 4-0 thrashing at Manchester United and face fellow strugglers Bournemouth in a crucial clash this weekend.