Reading suffered their first home defeat since November as Robbie Brady scored the only goal of the game to give Hull victory.
Alex Pearce and Shaun Cummings both went close for the home side who started the day above the Tigers.
Brady broke the deadlock midway through the second half, firing past Adam Federici from 18 yards out.
The win saw Hull leapfrog the Royals and move into the top six with their 14th win of the season.
Brady was preferred to Matt Fryatt in attack and Nick Barmby's selection was justified when he scored only his second goal of the season. Ironically his other also came against the Royals.
Reading, whose last home defeat came against Cardiff, started brightly and both Simon Church and Kaspars Gorkss headed wide.
Brady then brought a superb save out of Federici from a 30-yard free-kick which the Australian did well to tip over the bar.
Gorkss headed wide again before midfielder Brady, on loan from Manchester United, scored the only goal of the game.
The youngster raced on to a through ball from Paul McKenna and made no mistake to give Barmby his eighth win in charge.