The new deal will keep the 23-year-old at the club until June 2013.
Blaszczykowski joined Dortmund from Polish side Wisla Krakow in July 2007 and has made an impact at the Bundesliga side.
The winger admits coach Jurgen Klopp is one of the reasons why he signed the deal.
“I like the speed of the game and the system he plays,” he told the club’s official website.
