Helmes tore cruciate ligaments in his right knee during Wolfsburg's pre-season friendly game against Manchester City on Saturday that ended in a 2-0 victory for the Premier League champions.
The 28-year-old underwent a scan on Sunday which revealed that the injury he has sustained is similar to the one he suffered in 2009.
"Patrick was heading in the right direction and this is a bitter blow for him and for the whole team," Wolfsburg coach Felix Magath said on the club's official website.
"We will now all support Patrick so that he can get back onto the field as quickly as possible."
Wolfsburg will begin their Bundesliga campaign with an away game against Stuttgart on Sunday, August 26.