Cobh Ramblers lost their first league match at St Colman's since September 2006 as Bohemians moved to within four points of leaders St Patrick's Athletic with this important win.
The crucial goal came after 14 minutes when Neale Fenn set up Killian Brennan who shot past James McCarthy from close range.
The homeside were given the chance to equalise early in the second half after Ken Oman handled, but John Kearney's penalty was saved by Bohemians goalkeeper Brian Murphy.
This was the meeting of second-placed Bohemians and second from bottom Ramblers, with the visitors unbeaten in their five away matches taking on the homeside who were unbeaten at home in the Premier division, and without a defeat in St Colman's Park for since September 2006 against Dundalk.
Bohemians dominated the early stages and should have scored after just five minutes when Neale Fenn sent Glen Crowe in behind the home defence, but the striker's half-hit shot was saved by goalkeeper James McCarthy.
But Pat Felnon's side hit the front on 14 minutes, Fenn again involved as he crossed for Killian Brennan to control the ball at the far post, beat full-back Alan Carey and roll the ball past McCarthy.
In-form Fenn - who is currently keeping Jason Byrne on the substitutes' bench - went close again after 20 minutes when his low shot was just off-target, and Stephen Henderson would have been glad to get his team to the dressingroom just a goal behind at the break.
Cobh had a great opportunity to equalise nine minutes into the second half when they were awarded a penalty-kick, after defender Ken Oman handled Michael Mulconry's cross in the penalty area.
But John Kearney's left-footed strike from the spot was brilliantly saved by Brian Murphy who dived to his left to touch away the midfielder's shot, which added to Kieran O'Reilly's miss from the spot against UCD in the last home game.
So whilst Cobh's long unbeaten home run has ended, Bohemians have won five and drawn one of their six matches on the road in the league this season.
COBH: McCarthy; Carey, Guthrie, Murray, J Meade; Mulconry, J Kearney, Coleman, O'Shea; O'Reilly, O'Neill.
Substitutes; Long and Cambridge for Kearney and O'Reilly both 75 mins, Lally for O'Shea 83.
BOHEMIANS: Murphy; Powell, Burns, Oman, Heary; Brennan, Cronin, O'Donnell, Kelly; Growe, Fenn.
Subs; Byrne and McGuiness for Crowe and Oman (inj) both 66 mins, Rossiter for O'Donnell 79.
Referee: H Whorisky (Meath).
