The Ulster Ravens and Bedford Blues shared out six tries, but the place-kicking contribution of Canadian international James Pritchard proved crucial for the hosts at Goldington Road on Saturday.
A 2,105-strong crowd watched Bedford come from behind to earn their first victory in Pool C of this season's British & Irish Cup.
Full-back and captain James Pritchard played a key role, kicking five penalties and converting tries from scrum half Will Chudley and replacements Ollie Dodge and Joe Clark.
A stomach bug in the Ulster camp forced Jamie Smith and Robbie Diack to remain behind in Belfast in case they were needed for the province's Heineken Cup clash with Bath.
Into the team came Jonny Shiels and Scott LaValla and while both players managed to score tries, Ulster badly fell away in the second half as they coughed up a 17-6 half-time lead.
Gary Longwell's side, who scored a bonus point win over Swansea in October, fell behind to two early penalties from Pritchard.
The Ravens then built some pressure through their forwards and ex-Leinster man Brendan Burke had to be on his toes to defend a chip kick. The series of attacks yielded a penalty for the visitors which out-half Paddy Jackson dispatched through the posts.
The Ulstermen moved 17-6 clear thanks to two quick-fire tries. The first came from hooker Niall Annett who was on the end of a well-executed drive from a close-in lineout. Jackson supplied the extras.
The Ravens made it count again up front when American international LaValla barged over after a flurry of phases in the hosts' 22. Jackson converted again for a 14-point advantage.
A late Bedford attack was thwarted and the home side also had lock Sean Tomes yellow carded as the first half came to a close.
However, Bedford, who lost 29-3 at Ravenhill last season, went on to dictate the second half. The Ravens lost winger Tommy Seymour to the sin-bin and Pritchard converted the resulting penalty kick.
He added two more to really put the pressure on the visitors, and the Ulster defence gave way to allow replacement centre Dodge claim the Blues' first try.
Scrum half Chudley broke off the back of a ruck to score their second and a third followed from replacement hooker Clark, after a good break from out-half Sharp. Pritchard slotted the three conversions to maintain his 100% record.
The shellshocked Ravens salvaged some pride with a late try from Shiels who dived over after Bedford were caught for numbers out wide.
Nothing could disguise the Ulstermen's disappointment at the final whistle. They let this result slip from their grasp in a disappointing second half display, and will hope to bounce back at home to Moseley next Friday (kick-off 4pm).
Referee: Sean Brickell (Wales)