Donal O'Brien's first goal for Finn Harps was enough to give the Donegal side their first league victory over neighbours, Derry City.
The former Derry City player headed in a cross from Pascal Vaudequin in the 79th minute to seal victory for Finn Harps.
James Mulligan should have put the home side ahead in the fourth minute, but he shot straight at Tony O'Dowd. The Derry City keeper made another fine save in the 18th minute when he pushed away Davy Dowling's close range header.
Derry's first real threat came in the 58th minute when Jody Byrne had to make a fine save from James Keddy's free kick.
A minute later, Mulligan blazed over the bar from 10 yards, but Finn Harps' nerves were finally eased when O'Brien broke the deadlock 11 minutes from time.
Finn Harps: Byrne, Vaudequin, Minnock, Boyle, Bradley, O'Brien, McGrenaghan, McGettigan, Dowling, Mulligan, T Callaghan. Subs: G Callaghan for Mulligan (88 mins).
Derry City: O'Dowd, Doherty, Brunton, Taggart, Curran, Dykes, Bell, Hegarty, Coyle, Small, Keddy. Subs: Beckett for Small (70 mins), Kelly for Doherty (75 mins).
Referee: P McKeown (Dublin).
:quality(70)/cloudfront-eu-central-1.images.arcpublishing.com/irishtimes/YVIRIOZQ35EWRPZXR27KGMO6YU.png)