Ceri Sweeney's penalty gave holders Cardiff Blues victory in a repeat of last season's Anglo-Welsh Cup final.
Gloucester led 16-13 at the break at Kingsholm with Gareth Delve and Adam Eustace tries, plus a penalty each from Nicky Robinson and Freddie Burns.
The Blues replied through Xavier Rush and eight Sweeney points. After the break Sweeney traded shots with Burns.
Sam Norton-Knight's try put the Blues ahead and two Carlos Spencer penalties boosted the hosts, but Sweeney won it.
Gloucester coach Bryan Redpath:
"One of the things we talk about is if we create problems, we create points. When we go outside of that and go on our own agenda we cut our own throats and it has been happening too long.
"There is no excuse culture - you can't hide from it; it is as clear as night and day. We made two set-piece defensive errors.
"We missed Rush for his try and for the second try off the base of the scrum we were just chasing across the field and the guy steps inside and scores - two individual errors and it cost us 14 points."
Blues coach Dai Young:
"To come to Kingsholm is always difficult, it was a tight game and it could have gone either way right up until the end.
"From our point of view we are thrilled to come away from here with the right result.
"I thought we showed a real togetherness, a real commitment to the cause and a real determination to get that victory.
"On a couple of occasions they got their noses in front but we stuck to our game plan and got what we deserved."
Gloucester: Burns, Simpson-Daniel, Trinder, Molenaar, Vainikolo, Robinson, R Lawson, Doran-Jones, S Lawson, Somerville, James, Attwood, Eustace, Strokosch, Delve. Replacements: Satala for Burns (61), May for Simpson-Daniel (54), Spencer for Robinson (19), Capdevielle for Doran-Jones (41), Qera for Strokosch (42). Not Used: Dawidiuk, Thomas, Pasqualin.
Sin Bin: Strokosch (33).
Cardiff Blues: Norton-Knight, Mustoe, G. Thomas, Evans, Czekaj, Sweeney, Rees, Morris, R. Williams, Filise, Jones, Morgan, White, Sowden-Taylor, Rush. Replacements: D James for Evans (67), Hobbs for Morris (44), Navidi for Sowden-Taylor (48).
Not Used: R James, Andrews, Down, Allinson, Flanagan.
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