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.
Hull City 24 Gulacsi 02 Rosenior 03 Dawson Booked 05 Chester 06 Hobbs 04 McKenna 07 Stewart 08 Evans (Dudgeon - 87' ) 10 Koren 09 Mclean 12 Fryatt Substitutes 01 Basso 15 McShane 19 Dudgeon 14 Cairney 22 Adebola Leicester City 01 Schmeichel 02 Peltier 03 Konchesky 05 Mills Dismissed 06 Bamba 10 King 11 Dyer 19 Wellens 23 Danns (Gallagher - 63' ) 20 Beckford (St. Ledger - 30' ) 35 Nugent (Fernandes - 68' ) Substitutes 21 Weale 12 St. Ledger 26 Fernandes 07 Gallagher 09 Howard