Falkirk are now assured of a first ever crack at European competition
Tam Scobbie and Scott Arfield were on target as Falkirk set up a Scottish Cup final meeting with Rangers.
Scobbie knocked in a Neil McCann free kick with his shoulder early in the second half, with the Dunfermline defence posted missing.
The First Division side from Fife battled gamely but rarely threatened.
And the Hampden contest was settled late on when Arfield converted a penalty, following a clumsy trip on McCann by substitute Greg Ross.
Falkirk, who won the trophy in 1913 and 1957, were last in the final in 1997 when they lost out to Kilmarnock.
Win or lose on 30 May, John Hughes's side, who prop up the Scottish Premier League table, will take part in next season's Europa League, with Rangers already certain of a continental adventure.
The lack of pace in both sides was painfully apparent and a playing surface that cut up badly also contributed to a poor spectacle, watched by just 17,124 fans at the national stadium.
However, Falkirk were deserving winners, having created the best of the game's few chances.
The Bairns looked more assured in possession throughout but the Pars were full of energy and their robust tackling made sure the top flight team could not settle into a passing rhythm.
Powerful Falkirk striker Michael Higdon was first to threaten with a skidding shot from 22 yards which clipped the outside of the post
Soon after, Scott Arfield tried his luck from distance but Paul Gallacher had a comfortable job in palming it away to safety.
Arfied then got on the end of a Higdon knockdown only to see his tame header easily scooped up by the Pars keeper.
Dunfermline only had one brief glimpse of goal in the first half and Graham Bayne fluffed a great chance to divert an off-target shot from Alex Burke.
Five minutes before the interval, the ball fell invitingly for Carl Finnigan on the stretch but Gallacher made a fantastic diving block to make the point-blank save.
The second half was nine minutes old when McCann curled a delicious free kick into the penalty area and Scobbie stormed through the static ranks of Pars defenders to knock the ball into the net with his shoulder as he mistimed his header.
Dunfermline responded with a long range effort from Jamie Mole and a header from Rory Loy, which flew over, while McCann shot wastefully high on a Falkirk counter-attack.
With just two minutes remaining, an ugly scramble in the Dunfermline penalty area was interrupted when Ross upended McCann and Arfield confidently stroked home the resultant spot-kick.
Higdon thought he'd claimed a third goal for the Bairns but Gallacher made another excellent stop to claw away the striker's header from underneath the crossbar.
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