Both teams were hampered by errors in the wet and under lights but Gloucester made fewer and scored their tries at exactly the right moments to seal a crucial victory.
The opening 15 minutes were quite easily their most productive and sharpest of the contest and their two tries in this period owed a great deal to the expert running of Rory Lawson and the power and physicality of combatants like Olivier Azam, Jake Boer and Peter Buxton in front of him.
Gloucester were off and cooking as early as the fourth minute. Azam robbed an Irish line-out deep inside their own half, Luke Narraway helped the move forward and when play was recycled, Boer gave it extra momentum with a charge up the centre.
It was now the turn of Lawson to take over. The scrum-half broke blind across the face of the Irish defence, darted between two would-be tacklers and off-loaded to James Bailey, who showed good strength to score in the corner.
Their 7-0 lead was doubled almost instantly with a classic score of simplicity and directness that had Azam at its heart. Gloucester controlled their own line-out before Azam looped round, thundered forward and delayed his pass to perfection before sending Lawson to the sticks from 25 metres.
Gloucester were 12-0 ahead and blazing a considerable trail. But they then let Irish back into the contest through a series of mistakes at the breakdown - an area that was a continual source of frustration throughout - as the momentum dripped from their game.
Irish, competitive as ever at the contact area, poured plenty of men into the tackle situation but were rewarded with only one Barry Everitt penalty before the half-hour mark.
However, they scented a route back into the game through the yards churned up by Phil Murphy and the expert marshalling of Bob Casey and scrum-half Paul Hodgson. But their try involved a good deal of fortune after they had pounced on a Gloucester turn-over.
They shifted play to the left where Everitt kicked diagonally cross field and Riki Flutey was awarded the try despite the fact there appeared to be a knock-on.
Gloucester were in a trench battle now and required all the energy, tenacity and work-rate of Boer, the outstanding Buxton and the extra physicality provided by Azam to take on the Irish at their own game.
The second period was never as fluent as the conditions deteriorated and both teams struggled to find much continuity. Although Willie Walker made it 15-8 with a 44th minute penalty, Everitt landed three points soon after to leave the Irish trailing by four with 20 minutes to go.
It could have gone either way at this stage but with both teams finding it tough to get on the outside of defences because of the conditions, it was likely a mistake would settle the contest.
And that error came with nine minutes to go and Gloucester benefited. Irish looked to launch an attack from distance but Topsy Ojo's firm kick was brilliantly taken by James Simpson-Daniel and he sprinted 60 metres to dive home and seal the points.
The victory was massive for Gloucester and head coach Dean Ryan was delighted with the resilience and determined shown by his side.
"We obviously made some errors but I thought we showed a degree of maturity and smartness at key times that was crucial," he said.
"Our positional kicking game was very good when it needed to be and the two tries we scored early on were simple but hugely effective. We were physical, determined and controlled. Away wins in the Premiership are rare and to win against a team of Irish's quality is really pleasing."