Juan Manuel Leguizamon scored the only try of a scrappy Guinness Premiership contest in which Gloucester struggled to find a way to combat the Exiles' shrewd gameplan.
As at the Madejski Stadium in November, Gloucester struggled to make inroads from their line-out and threw away too much practicable possession as Irish penned them back.
Both Ludovic Mercier and his counterpart Riki Flutey scuffed early penalties into the wind, unable to capitalise on the first of the glut of errors which became the overriding memory of this game.
South African referee Jonathan Kaplan had plenty to deal with as he warmed up for his Six Nations appointments on a bitterly cold afternoon.
Irish picked their way towards Gloucester's five-metre line, eventually releasing their back line, only for Nils Mordt to fling a pass in front of Delon Armitage and turn the ball over to the home side.
Gloucester edged back upfield and when Irish pulled the scrum down, Mercier slotted his first three points with 18 minutes on the clock.
Flutey responded with a penalty of his own three minutes later when Gloucester failed to roll away from a tackle as Irish pounded their way straight back up the pitch.
Unable to master Irish's pack, Gloucester's made inroads when they broke quickly from the tight, and Adam Balding's pick-up from the back of the scrum sent Peter Richards on a mazy run, but the scrum-half failed to find Marcel Garvey with his pass and the play broke down.
As Irish pressured again late in the first half, Flutey kicked for position and his forwards recycled the line-out, piling over with Argentine number eight Leguizamon touching down and Flutey converting.
Another quick break off Adam Eustace's fine line-out take saw Gary Powell charge forward, but their advance halted again after the ball was pushed wide to James Simpson-Daniel.
Flutey added his second penalty at the start of the second half as Gloucester continued to search for some momentum.
Head coach Dean Ryan sent on centre Rudi Keil for his debut, with Simpson-Daniel moving to the wing in place of Garvey, while James Forrester returned from injury to replace Balding.
A switch from Keil to Mike Tindall enabled Simpson-Daniel to race towards the line only to be caught by Topsy Ojo, although the Exiles winger was sinbinned a few minutes later for killing the ball after James Bailey had scythed through the defence and was stopped three metres short.
But despite their late rally, all Gloucester could add were two further Mercier penalties which, with Flutey missing a 45m punt and a drop-goal, secured a losing bonus point for Ryan's men.
|Gloucester Rugby Score Card|
|London Irish Score Card|