كتب : Hatem Maher
Christian Timm opened the scoring eight minutes past the hour mark after unleashing a powerful shot that went into the back of the net.
He ensured the victory seven minutes from time after being set-up by Hungarian midfielder Tamas Hajnal.
Newly-promoted Karlsruhe moved to second place in the Bundesliga table 18 points while Schalke slipped to fifth spot on 15 points.
Title holders Stuttgart failed to ease their crisis following a 2-0 home defeat to Hanover.
Stuttgart, who suffered a 2-0 defeat to Barcelona in the midweek Champions League clash, had to play with 10 men for most of the game after defender Fernando Meira was sent-off for a delibrate handball.
Szabolcs Huszti notched twice to help the visitors grab a precious win.
Mohamed Zidan's Hamburg continued their fine form with a 1-0 away vicotry over Arminia Bielefeld, thanks to a strike from skipper Rafael van der Vaart.
Egyptian forward Zidan did not take part in the game as he sat on the bench.