Australian full-back Peter Hewat contributed 18 points as London Irish ended their three-match losing run in the GUINNESS PREMIERSHIP.
The victory provided a timely boost for Irish ahead of next Sunday’s home Heineken Cup quarter-final against French side Perpignan.
But they remain in eighth place in the Premiership after successive defeats at the hands of Gloucester, Wasps and Bath effectively killed off their hopes of a top four play-off place.
Hewat, restored to kicking duties after Irish had costly misses in the setbacks against Wasps and Bath, scored a try, three penalties and two conversions.
The other Irish tries came from hooker Stuart Mackie and centre Seilala Mapusua.
Bristol replied with a first-half penalty from fly-half Ed Barnes and a late try from right-wing Tom Arscott.
England scrum-half Shaun Perry, back in the Bristol side after the throat injury which forced him to miss the RBS 6 Nations, worked hard to get the visitors moving but they seldom posed a threat in attack.
Paul Hodgson, called into the England squad during Perry’s absence, had the better day, combining well with veteran fly-half Mike Catt, the steadying influence who dictated play for Irish.
Hewat’s opening 13th-minute penalty for Irish was cancelled out by Barnes before the home side broke the early deadlock with a try in the 23rd minute, inspired by winger Topsy Ojo whose pace was a constant problem for Bristol.
Ojo made the initial break and figured three more times in an attack which saw lock Nick Kennedy hauled down just short of the Bristol line before the winger supplied the final pass to put Mackie over from close range.
Hewat converted and landed a second penalty to send Irish in 13-3 ahead at half-time.
Bristol’s problems increased in the 49th minute when prop forward Jason Hobson was punished with 10 minutes in the sin bin for blatantly obstructing Hodgson during a promising Irish attack and Hewat kicked the resulting penalty, his third success from four attempts.
While Hobson was off the field, Irish stretched their lead after Hodgson kicked ahead down the right and Hewat won the race to touch down.
With victory almost certainly secured Irish withdrew Catt, with the Heineken Cup in mind, replacing him with Eoghan Hickey as they made a raft of substitutions.
Hewat linked up in attack again to draw the Bristol defence and lay on his side’s third try for Mapusua in the 65th minute.
There was an unusual substitution in the 74th minute when referee Dave Pearson limped off to be replaced by fourth official John Dennison.
With the game beyond their reach Bristol produced their most productive period of the match.
A series of attacks had Irish defending desperately but they finally cracked when Bristol’s Arscott raced over for a 78th-minute try in the right hand corner.