The 27-year-old, who arrived from Wisla Krakow in 2007 and has since gone on to make 168 appearances, scoring 25 goals and providing 41 assists, put pen to paper on a contract until 2018 on Monday.
"Kuba is an important cornerstone of our team, both sportingly and in terms of his character, and he was outstanding across Europe last season," said Dortmund's director of sport Michael Zorc.
"We are delighted to be able to form a long-term future with him."
Blaszczykowski has been capped 60 times by Poland and has developed into a key player for both club and country.
"I feel this is my second home," said the 27-year-old. "When my contract expires, I will be able to look back on over a decade with BVB.
"That's not something which you can take for granted in professional football nowadays."