Gloucester were first on the score sheet with a penalty from centre Henry Paul to take a 3-0 lead.
A tap penalty from David Humphreys got Ulster into Gloucester territory, but the pass failed to reach Roger Wilson.
Kieran Campbell conceded a penalty in the 29th, which Henry Paul successfully kicked from 40 metres. A third penalty was added in the 33rd minute after a collapsed Ulster scrum, giving Gloucester a 9-0 lead.
Ulster?s first score of the evening came in the 39th minute, when David Humphreys kicked a penalty from near the halfway line.
Gloucester?s Simon Amor then pulled Gloucester?s lead back to nine points with a drop goal into injury time in the first half.
Ulster thought they were heading into the break having cut Gloucester?s lead, when Tommy Bowe ran on to a crossfield kick from David Humphreys. However, he was adjudged offside by referee Nigel Whitehouse, a decision which did not please the Ravenhill faithful.
Half time score: Ulster 3-12 Gloucester
Six minutes into the second half, David Humphreys gave a repeat crossfield kick, which was again gathered by Tommy Bowe, before passing on for Bryn Cunningham to cross the try-line. Humphreys missed the conversion, but Ulster had cut Gloucester?s lead to four points, with the score at 8-12.
Gloucester then fought back and looked to have increased their lead when Marcel Garvey was close to scoring a try, but he knocked the ball on just short of the line.
Garvey then came close to scoring again, but Paul Steinmetz and Tyrone Howe combined to make a try-saving tackle.
Ulster then brought on ?fresh legs? with Andy Ward on as a replacement for Captain Cambpell Feather, Rowan Frost replacing Gary Longwell, and Paul Shields on for Rory Best.
A penalty from David Humphreys on 69 minutes cut Gloucester?s lead to a point, when he slotted over an excellent penalty from close to the touchline.
Four minutes later Ulster took the lead in the match, with another penalty from man of the match Humphreys, after a Gloucester infringement.
In the closing minutes the Ulster line was under constant pressure from Ulster. Simon Amor pushed a drop goal effort wide into injury time, and with Ulster?s defence holding strong, the Ravenhill crowd were left ecstatic as the referee blew the final whistle.
Final score: Ulster 14-12 Gloucester
The win extends Ulster?s winning run in the Heineken Cup at Ravenhill to 12 matches.
In the other pool six match this evening, Stade Francais defeated Cardiff Blues by 35 points to 16 points.
In the final pool matches next Sunday, Ulster travel to Cardiff to take on The Blues, whilst Stade Francais travel to Kingsholm to take on Gloucester. For Gloucester to qualify for the next stage of the competition, they need to secure a bonus point win.
Ulster: Cunningham; Bowe, Steinmetz, Maggs, Howe; Humphreys Campbell; S Best, R Best, Moore, Longwell, McCullough, Feather (capt), N Best, Wilson.
Replacements: Shields, McCormack, Frost, Ward, Doak, Larkin, Wallace.
Gloucester: Goodridge; Garvey, Fanolua, Paul, Bailey; Amor, Gomarsall; Bezuidenhout, Parkes, Vickery, Eustace, Brown, Boer (capt), Hazell, Balding.
Replacements:Elloway, Sigley, Wood, Buxton, Forrester Page, Mauger.
Referee: Nigel Whitehouse
Attendance: 11,435
Man of the Match: David Humphreys
