A header by defender Niklas Süle was enough to see off Hertha Berlin and send Hoffenheim third. Later on Sunday, Anthony Modeste continued his remarkable scoring run with a hat trick against Hamburg.
Hoffenheim 1-0 Hertha Berlin
A towering header by defender Niklas Süle gave Hoffenheim a vital win over fellow high-fliers Hertha Berlin.
After a bright start by Hertha, Hoffenheim took control of the game with Lukas Rupp going clean through and seeing his shot saved well by an inspired Rune Jarstein, and Pavel Kaderabek heading against the bar.
Hoffenheim continued to threaten the Hertha goal and took a deserved lead through Süle, who headed in Kerem Demirbay's pinpoint cross.
Jarstein kept Hertha in the game with some fine saves, with Kramaric wasting a fine late chance to make the win safe.
But Hoffenheim were good value for their win in the end, as they leapfrog Hertha to move third in the table, two points behind second-placed Leipzig.
Cologne 3-0 Hamburg
(Modeste 61', 82', 86')
Anthony Modeste continued his remarkable scoring run with a stunning 25-minute hat trick as Cologne inflicted further misery on 10-man Hamburg.
Modeste struck the base of the post with a penalty a few minutes before halftime after Yuya Osako was hauled down in the box.
But the game's turning point came when Hamburg striker Bobby Wood was shown a straight red card for an elbow off the ball on Dominique Heintz.
Three minutes later Modeste struck for Cologne, applying the slightest of touches to an inswinging cross by substitute Simon Zoller.
Modeste was celebrating again when he nodded in Marcel Risse's cross at the near post, putting Cologne's victory beyond doubt, before beating the offside trap to slide in a third - his 11th in the Bundesliga this season.
The result sends Cologne fourth and leaves Hamburg rooted to the bottom of the table.