Joe Gelhardt was given far too much space early on, and he made use of that to give the Tigers the lead with barely two minutes on the clock in United’s first away game of the season.
But the U’s got back level before the 10-minute mark, as Will Lankshear struck a first-time volley home from near the penalty spot.
The Tigers continued to launch attacks though, and more questionable defending from United allowed Matt Crooks space to restore the lead for the hosts, but Cameron Brannagan found a second U’s leveller six minutes later with a good strike from outside the penalty area.
As the game looked like it was heading towards a draw, Oli McBurnie stayed calm to find the net four minutes into stoppage time.
Gary Rowett opted for the same side which lost at home against Portsmouth on the opening weekend, meaning returns to the starting line-up for Elliott Moore, Brodie Spencer, Greg Leigh, Will Vaulks, Stan Mills and Mark Harris after the Carabao Cup victory over Colchester United.
The first half was crammed full of goals, with the Tigers taking the lead a little over 60 seconds into the game.
Gelhardt was afforded far too much space by a combination of Leigh and Moore to make his way into the right channel of the penalty box, before then squeezing the ball through a gap inside the near post.
Leigh had to make an excellent block to thwart Crooks only a few minutes later, as United were exposed again at the back, although the offside flag was raised, but Leigh wasn’t to know that.
In their first attack of any substance, the U’s pulled themselves level, as Tyler Goodrham did brilliantly to keep the ball in play and hook it back to Lankshear close to the penalty post, with the Tottenham Hotspur loanee hitting a lovely first-time volley for his first United goal.
Kasey Palmer saw a free kick clip the wall 20 yards from goal, and then Mills pinged a low strike from outside the box, but Ivor Pandur was able to claim the effort.
With 20 minutes on the clock, the Tigers went back in front after working the ball well round a static U’s defence, leaving Crooks the task of finishing low into the corner.
Jamie Cumming then had to be alert in order to punch away a Palmer corner whipped in towards the goal line.
Just after the midway point of the first half, United battled back level again when a long throw-in was cleared as far as Brannagan on the edge of the box, and the midfielder found the corner with a nicely struck right-footed volley.
The chances kept coming for the hosts though, with a dangerous ball across the six-yard box reaching Gelhardt at the back post, but he could only find the sidenetting.
The U’s had opportunities to go in front in the final five minutes of the half, with Lankshear drilling a left-footed effort narrowly wide from the edge of the area.
An excellent ball from Brannagan got Mills away down the right, but the winger was unable to pick out Harris from a promising position.
At the other end, Palmer slid through Oli McBurnie, whose strike was deflected out for a corner, while Gelhardt lined up a left-footed shot from range, but it was claimed by Cumming in the last bit of action in the first half.
Rowett introduced Sam Long for Harris at the break, ensuring a change of shape to a 3-4-3 formation when in possession.
Twelve minutes into the second period, Rowett made further alterations, as Siriki Dembele and Matt Phillips replaced Goodrham and Mills.
Phillips thought he had scored not long after, when he blasted a low strike which went narrowly wide of the far post via a smart save from Pandur.
The ball reached Vaulks from a Dembele corner with a little over 20 minutes to go, and the midfielder swept a low strike into the gloves of Pandur, who claimed it at the second attempt.
Gelhardt caused United problems all afternoon and he made a darting run before drawing a good save out of Cumming at his near post in the final quarter of an hour.
Gelhardt then avoided a couple of challenges and stung the gloves of Cumming, who fisted away the strike from the Leeds United loanee.
The U’s needed Moore to make a brilliant block and thwart former United loanee Kyle Joseph after a low cross from the right just before seven minutes of stoppage time were signalled.
Four minutes into injury time, McBurnie took his time to get the ball under control from a left wing cross and then picked his spot with a composed finish.
Hull City (4-2-3-1): Pandur; Drameh, Egan, Hughes, Giles; Crooks (Slater 87), Lundstram; Gelhardt (Joseph 87), Palmer (Kamara 67), Ndala (Akintola 67); McBurnie (Famewo 90+7).
Unused subs: Phillips, Williams, Brown, McCarthy.
Booked: Crooks.
[Oxford United](http://www.thisisunited.com/) (4-4-2): Cumming; Spencer, Helik, Moore, Leigh (Currie 85); Mills (Dembele 57), Vaulks, Brannagan, Goodrham (Phillips 57); Harris (Long 46), Lankshear (Bradshaw 76).
Unused subs: Ingram, ter Avest, Johnson, Sibley.
Booked: Spencer.
Referee: Andrew Kitchen (County Durham)
Attendance: 20,667 (TBC away)