Austin McCann's third-minute goal gave Dunfermline the points at Hibernian, with whom they are now level in the Scottish Premier League table.
The former Hearts defender converted a Paul Willis cross from close range for his first goal in more than 100 appearances for the Pars.
Dunfermline almost added another in 36 minutes when Ryan Thomson's knockdown found Andy Kirk, who shot just wide.
Paul Gallacher saved well from Hibs' Garry O'Connor and David Wotherspoon.
Hibs recorded three home wins in February, but have since won only once at Easter Road - the defeat of St Johnstone on 28 September.
For Jim McIntyre's side, it was only their third win of the season and their first since August.
O'Connor was joined in the home attack by Leigh Griffiths and Junior Agogo, with Ivan Sproule and Akpo Sodje in reserve, yet they looked blunt.
The Pars, meanwhile, were workmanlike and worthy of victory through the one moment of quality in an otherwise sub-standard game.
O'Connor shot straight at Gallacher in the second minute and seconds later the home side were a goal down, when McCann was rewarded for his run from deep by getting on the end of Willis's cross.
Hibs attempted to respond, but the final ball continually let them down.
A Thomson knockdown made its way to Kirk, whose drive deflected narrowly wide of the post.
From the resulting corner Andy Dowie headed over and his complaint of being impeded in challenging for the ball was dismissed.
Gallacher saved from Griffiths after Wotherspoon's attempted cross and O'Connor's bid to follow up was blocked as Hibs missed the chance to draw level at the interval.
After the break, a Wotherspoon cross was met by Griffiths, whose looping header was tipped over by Gallacher before O'Connor mis-cued a shot after the on-loan Wolves striker's cut back.
Griffiths missed a glorious opportunity after turning inside the edge of the area following Paul Hanlon's pass, the striker dragging his shot wide with only Gallacher to beat.
After Agogo was replaced by Sproule, Hibs defender David Stephens did well to block Liam Buchanan's run into the box.
Hanlon became the first player booked for persistent fouling before Gallacher turned O'Connor's header from Wotherspoon's cross over the bar.
Richie Towell came on for Lewis Stevenson as Hibs looked for a fresh creative spark and with 11 minutes remaining Sodje was introduced for the disappointing O'Connor. But Hibs' troubles continued.
Wotherspoon, shaky in defence but prominent in attack, had an effort saved by Gallacher before blasting the follow up over.
Danny Galbraith shot well wide before Gallacher turned a Griffiths shot around the post in the first of four minutes of stoppage time.
Goalkeeper Graham Stack came up for the resulting corner, which was over-hit and the Pars prevailed as Hibs left the field to jeers from the home crowd.