The 30-year-old player joined the Bundesliga side after leaving Qatari club Al-Arabi SC.
Dejagah, who becomes the Wolves’ fifth new arrival in the January transfer window, has signed a six-month contract until the end of the season with the option of a further year.
"I'm delighted to be back in Wolfsburg and I'm looking forward to playing in the Bundesliga again," Dejagah told the club's official website.
"We're in a difficult situation right now and I want to help the team get out of trouble as quickly as possible."
A Germany-born Iran international represented his country at the 2014 FIFA World Cup in Brazil.
The right-sided attacker played for Wolfsburg between 2007 and 2012 and helped them win the Bundesliga in 2008/09 before leaving for English side Fulham FC in 2012.
Dejagaha scored 18 goals in 132 Bundesliga appearances in his first spell for the club.