Gladbach, who needed a relegation play-off last season to stay up, have seven points from three games.
With new signing, former West Ham United midfielder Thomas Hitzlsperger, in their lineup Wolfsburg struck after 12 minutes when Japanese Makoto Hasebe finished off a good move.
Gladbach needed only three minutes to draw level. Visiting defender Simon Kjaer slipped just outside the box and Raul Bobadilla picked up the loose ball before feeding Reus who tapped in from close range.
"It was almost good for us to concede a goal," said Lucien Favre who took over as Gladbach coach late last season.
"We reacted instantly and were by far the better team," he told Sky television. "We played extremely well and could have won by a much bigger scoreline."
The hosts looked sharper after the equaliser and their dominance paid off when Reus was brought down and Belgian defender Filip Daems converted a 32nd-minute penalty.
Argentine Bobadilla added another goal on the stroke of halftime, heading in a Juan Arango cross, before Reus grabbed his second goal of the evening with a fine volley at the far post on 67 minutes.
"Nothing worked for us tonight," Wolfsburg midfielder Christian Trasch told reporters. "We started well and deserved to go a goal up but then we made mistakes.
"Losing 3-1 or 4-1 doesn't really make a difference. Our performance was nothing to be proud of."
