Pompey were left to rue missed chances as Hull stole three points at Fratton Park.
The Tigers nicked a 3-2 win to continue a frustrating start to the year for the Blues.
Steve Cotterill's men racked up chance after chance in the first-half, but went in one down after a controversial penalty from Jimmy Bullard.
Greg Halford was harshly penalised for a foul on Cameron Stewart after 21 minutes.
The likes of Hermann Hreidarsson, David Nugent, Kanu and Liam Lawrence all had great chances.
Pompey levelled from the spot after 57 minutes after Liam Lawrence converted after being pulled down by Anthony Gerrard.
It looked like the Blues would take control from there, but two quick-fire goals changed the game.
Sub Matty Fryatt had the freedom of the area to put his side in front after 72 minutes.
Then Nick Barmby put daylight between the sides three minutes later.
Greg Halford set up a grandstand finale with 14 minutes left, but Pompey couldn't salvage a point late on.
That leaves Pompey in 18th place on 30 points from 24 games.