It was Livingston's seventh successive defeat and it was down to a goalkeeping error from Ludovic Roy.
The hosts started in positive fashion but, just when they didn't need it, back-up goalkeeper Roy gifted the Pars the only goal after 12 minutes.
A Mark Burchill cross took a wicked bounce in front of the goalkeeper and he bundled the ball into his own net under no pressure.
Dunfermline lost Noel Hunt four minutes later with a thigh injury and he was replaced by Andy Campbell.
Roy did not instil confidence and he misjudged a Darren Young free-kick midway through the first half and Livi were lucky there was not a Dunfermline player waiting at the back post.
Andy Tod was yellow carded for bringing down David McNamee just a foot outside the area but Derek Adams lashed the free-kick high over the top.
Burchill looped a shot over the top at the other end but chances were few and far between.
Dave MacKay headed a Wes Hoolahan corner just a yard too high, but visiting keeper Bryn Halliwell was not called upon to make a save in the first half.
Paul Lambert's men tried to come back in the second half but had little threat up front until Steve Hislop came on.
He saw a header hooked off the line by Jamie McCunnie as Livingston threw everything forward.
Harald Pinxten had the final chance to salvage a point in injury-time but his 20-yard shot was straight at Halliwell.