Kicking machine Tom Homer booted another 19 points as London Irish hung on to survive a spirited Exeter Chiefs comeback at the Madejski Stadium.
Tries from home centres Joe Ansbro and Shontayne Hape earned Irish their victory platform.
Visiting full-back Luke Arscott's try for Exeter gave the Chiefs hope before Ignacio Mieres' fifth penalty narrowed the gap to four points.
But another penalty for Homer, the Premiership's top scorer, sealed it.
Irish were never comfortably ahead, even though they led 19-9 at half-time, against an Exeter side who, as they showed in beating Sale four weeks ago when trailing by 16 points at the break, never give in.
But Irish coach Toby Booth had to defend a first-half incident which could have landed England star Delon Armitage in more hot water.
Armitage has only just returned to action with Irish this month after a five-week ban for a dangerous tackle on Bath wing Tom Biggs and a concurrent ban for striking lock Dave Attwood with his knee in the same match on 29 October, earning his fourth suspension in 2011.
The England full-back was on song, but left Argentinian fly-half Mieres shaken for a few minutes on the touchline when he clattered into him, with an arm around his head as he fielded the ball by his own 22.
London Irish coach Toby Booth:
"[Armitage] went in for a tackle from behind and, as the player has bent down, he has gone up over the top of him. It is a penalty at most in my in opinion. But, as always, because of what has gone before, people will have a closer look.
"We took our chances and I'm delighted about that. We started exceptionally well. We took the game by the scruff of the neck and the reason why we didn't dictate was probably because the penalty count was two to one in their favour.
"We have made life more difficult for ourselves than we needed to but make no bones about it, we are delighted with the outcome. We just could have been a bit smarter. What I would say about the contest is that there was a lot of endeavour from both sides and, from a crowd point of view, it would suggest to me that it was an enthralling contest. People were positive and that has to be good for everyone."
Exeter Chiefs head coach Rob Baxter:
"It certainly dazed him. There is definitely an arm over the top. That is not alleged. You can see that pretty clearly. The touch judge was in a pretty good position and he gave his worth on what he thought it was. I'm not too concerned about that, you just have to get on with it and play.
"Ultimately, that first 20 minutes, we didn't play enough. In reality, we are a team which is learning. The only goal we gave ourselves this season was to be better. We came here last year and got nothing, now we have got a losing bonus point.
"We are just a better side when we go for it. My job is to free these guys up and make sure we go for it every week. By doing that, we will win more games than we lose."
London Irish: D Armitage; Ojo, Ansbro, Hape, Homer; Shingler, Allinson; Dermody, Paice, Ion; Evans, Garvey; Danaher, Gibson, Thorpe.
Replacements: Corbisiero for Ion (53), Buckland for Paice (55), Gray for Thorpe (64), Hodgson for Allinson (70), Casey for Garvey (74), Halavatau for Dermody (79).
Not Used: Thompstone, Jarvis.
Exeter: Arscott; Camacho, Sestaret, Dollman, Jess; Mieres, Thomas; Tui, Alcott, Mitchell; Hayes, Bentley; Baxter, Scaysbrook, Phillips.
Replacements: Shoemark for Dollman (41), Muldowney for Tui (42), Sturgess for Bentley (43), Clark for Alcott (49), Andress for Mitchell (53), Barrett for Thomas (62).
Not Used: Johnson, Steenson.
Referee: D Richards (RFU).