Simon Whaley put Preston ahead, scoring for the third successive away game with a long-range shot low into the corner.
Just before the break Preston skipper Youl Mawene seemed to get the final touch after a desperate scramble in his own goalmouth, levelling the scores.
Preston had the better of the second half although substitute Darryl Duffy twice went close for the home side.
Hull manager Peter Taylor:
"I think it's been a realistic season for us and we've got used to this division as it has gone on.
"I thought we gave away a really poor goal but we recovered and I was pleased with the way we played.
"Preston will be very dangerous in the play-offs because they are a very organised team."
Preston boss Billy Davies:
"We've got one or two guys coming back at the right time, and when you have the best players available, you always have a chance.
"Simon Whaley has a tremendous goalscoring record and is a young man who is still learning. When we get a couple of players back, we will have several threats in our team for the play-offs. Whaley had great energy, is full of tricks and has a great eye for goal.
"The most important thing is that we're in the play-offs, and we don't mind who we get."
Hull: Myhill, Wiseman (Thelwell 87), Cort, Delaney, Rogers, Green, Welsh, Andrews, Ellison (Paynter 83), Fagan (Duffy 64), Parkin.
Subs Not Used: Duke, Dawson.
Goals: Mawene 43 og.
Preston: Nash, Mears, Wilson, Mawene, Hill, Sedgwick, Stock, Jarrett (McKenna 82), Whaley, Lewis Neal (Agyemang 70), Dichio.
Subs Not Used: Chris Neal, Alexander, Hibbert.
Booked: Mawene, Dichio.
Goals: Whaley 33.
Att: 19,716.
Ref: T Bates (Staffordshire).