The fight was scored 114-114, 116-113 and 116-112 to the Russian, but Huck produced a brave performance over the 12 rounds in Stuttgart.
Having defended his WBO cruiserweight title eight times, this was 27-year-old Huck's first fight at heavyweight.
Saturday's win leaves the 32-year-old Povetkin with a record of 24
victories, including 16 knock-outs and no defeats.
After a lively first round, Huck was warned for holding by referee Luis
Pabon while Povetkin caught the Serbian-born German with two right hooks in the second.
Povetkin landed several powerful body shots in the third as he managed to
briefly pin Huck to the ropes, but the challenger landed a good right.
Huck clearly took the fourth with several shots on two separate occasions,
but the challenger was again warned for a punch to the back of the head.
Huck went toe-to-toe with the champion midway through the seventh, and a clean shot to the chin had the Russian wobbling.
At the start of the eighth, Povetkin landed several good head shots of his
own and when a small cut opened under Huck's left eye in the 11th, the Russian had Huck in real trouble.
Huck still managed a full shot to the face in the 12th and the challenger
finished with a flurry of punches with both fighters exhausted at the final
British boxer Dereck Chisora, who caused controversy by brawling with
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ex-champion David Haye last weekend in Munich, returned to Germany and was ringside in Stuttgart to watch the fight.
Having lost to WBC heavyweight champion Vitali Klitschko last Saturday,
Chisora remains under investigation by Munich police for his part in the brawl during the post-fight press conference at which he threatened to "shoot" Haye.
Chisora faces a hearing before the British Boxing Board of Control in London on March 14.