Dortmund's city government said the 250-kilogram British bomb was defused today.
The bomb had been unearthed after authorities evaluated aerial photos ahead of planned construction work, and a 250-metre radius around the site was evacuated.
Because the stadium was inside the evacuated area, the club relocated the news conference of coach Juergen Klopp ahead of the Ruhr derby against Schalke to another facility.
Unexploded ordnance from WWII is still frequently found in Germany, and that regularly results in temporary evacuations such as today's.