The 28-year old American defender has penned a two-and-a-half-year deal with the Bundesliga strugglers after four years in Denmark where he helped Nordsjaelland take out last season's Super Liga title.
"I would like to make my sporting contribution, so that we achieve our goal of staying up in the second half of the season," he told his new club's official website.
"I watched the DfB-Pokal (German Cup) match against Bayern Munich yesterday and was impressed by the great atmosphere despite the defeat. I can't wait to get in that atmosphere myself."
Apart from Nordsjaelland's first-ever Danish title, Parkhurst also won the 2010 and 2011 Danish cups whilst competing in this season's Champions League group stage.