The 27-year old former Chelsea player will join the Craven Cottage side for the next two seasons.
Schurrle won the World Cup with Germany in 2014 but did not make the squad for this summer’s tournament.
“I can’t wait to get started,” he said via BBC. “I have to fight for my place and I have to show my quality so that I can be a member who really helps the team.”
Schurrle played for Chelsea from 2013-15 and won a Premier League winners medal in 2015 despite leaving the club for Wolfsburg part-way through the season. He has been at Dortmund since July 2016 and has 57 caps for Germany.