Robert Koren's late winner ruined Nigel Pearson's return to Hull just 18 days after he left the club for a second spell as Leicester manager.
Koren curled an 88th-minute effort into the top corner to lift Hull above their opponents in the Championship table.
Matt Fryatt put the Hull ahead from the penalty spot after Matt Mills was sent off for a foul on Aaron Mclean.
Paul Konchesky levelled before half-time from 20 yards and that looked good enough for a point before Koren scored.
The home side perhaps deserved the win after Cameron Stewart and Paul McKenna tested Foxes keeper Kasper Schmeichel, who also turned Andy Dawson's volley round the post.
But Pearson, who received a predictably hostile reception from the home fans, may point to a harsh-looking dismissal of his captain as the turning point.
Mclean broke through on goal only for Mills to make a superb block and as Mclean got up for a second attempt, he appeared to slip over with Mills nowhere near.
Fryatt sent Schmeichel the wrong way but Konchesky's curling effort restored parity.
Hull bossed the second half but were forced to wait until the latter stages to secure the victory via Koren's superb strike.