Reading came from behind to snatch the points at Hull in Liam Rosenior's first home match in charge.
An unmarked Jacob Greaves headed the Tigers ahead inside 10 minutes but before the break Yakou Meite levelled from close-range on his 150th Royals appearance.
It looked set to end all-square but four minutes into added time Andy Carroll flicked on a Tom Ince cross which went in off a defender.
It was a first win in nine games on Humberside for the Royals while have lost seven of their last eight home games.
More to follow.