Hamburg got the better of Mainz in a tense battle at the HSV-Arena, with a second-half goal from Heung-min Song earning Thorsten Fink's side all three points.
There were few chances between two sides who did not appear to want to do each other any harm, resulting in a tactical exchange which was decided in the 63rd minute by the South Korean midfielder.
The result took Hamburg level on points with their opponents with both sides still well-positioned just below the top six places.
Mainz came into the game with a three-point advantage over their hosts, but did not seem to want to force that issue as they played a cagey game.
Marcel Risse did have the first shot of the game for the visitors in the sixth minute, but after he missed the target, nobody else dared try to find it.
That was, however, until Marcell Jansen tested Christian Wetklo's alertness in the 20th minute, and the Mainz goalkeeper responded positively.
It looked like a goal was not going to come until Maximilian Beister sent the ball into the danger area on the volley and Song, from a disputably offside position, tucked the ball in from close range.
Mainz had to abandon their defensive tactics and Rene Adler was called into action a few times.
However, the visitors failed to truly test the Germany international and Hamburg held on to the points without using up too much energy, not needing a second goal, although they rarely looked like they could provide one either.