A superb curling 20-yard shot from veteran Russell Latapy opened the scoring for Falkirk on 44 minutes.
But Gary Wales was on hand to grab a quick equaliser seconds later when he slid in to slam the ball home after Frazer Wright's header had been saved.
Di Giacomo struck in the 87th minute when his miscued shot confused Bairns goalkeeper Scott Higgins.
It was hard luck on Falkirk, who had the best of the chances in an exciting game.
Wales registered the first effort on target on 15 minutes when his header from Gordon Greer's cross was held by Scott Higgins at his near-post.
On 26 minutes, a quick Kilmarnock attack saw
Wales lay off to the on-rushing Danny Invincibile
but his drive was held by Higgins at the second
attempt.
Victor Lima's swerving 22-yard effort looked net-bound until Killie's Graeme Smith made an excellent finger-tip save to divert it past the post.
Pedro Moutinho then lifted a shot over after a mix-up in the Killie defence.
Falkirk then produced a brilliant passing move with Latapy feeding Alan Gow.
The former Airdrie man quickly flicked the ball through to Moutinho but Smith blocked his lofted strike.
A moment of magic from the 38-year-old Latapy broke the deadlock.
Gow fed Latapy just outside the box and the
Trinidadian dipped his right shoulder before curling
a delicious shot into the top right-hand corner.
But Killie were immediately level. From a Leven corner, Wright's powerful header was saved by Higgins but Gary Wales swept home the rebound.
Lima sent a hooked shot just over then Moutinho turned well before driving a shot into Smith's body.
Falkirk were on top again and almost profited after Smith dropped Latapy's corner, but Killie scrambled clear.
As the game flowed at pace, Higgins made another solid stop from Steven Naismith on the hour after Invincibile's tricky run.
With the game heading for a draw, Kilmarnock
grabbed all three points with a lucky goal.
Leven's cross picked out Paul Di Giacomo who hit a left-footed shot into the ground.
With Naismith jumping over the ball in front of Higgins, the Australian was helpless as it bounced past him.
Latapy responded with another long-range strike wide but Killie held on for the victory.
Sandy Ferguson's Bairns match pic's are - Here





