The clubs meet twice inside four days, but it will be Jim Jefferies' side who approach the last-four tie at Fir Park with the greater optimism after a merited win.
Colin Nish - restored to the starting line-up - gave Kilmarnock the lead after 22 minutes to end a bright start by the Bairns, before Steven Naismith's 10th of the season wrapped up the points six minutes later.
The result allowed the Rugby Park side to leapfrog their opponents into the top six of the SPL table and continue their unbeaten streak against Falkirk which stretches to February 1996.
Bairns boss John Hughes had been boosted by the presence of Darren Barr in his line-up - after the defender's controversial red card at Hearts was overturned - but he appeared to miss the influence at the back of the suspended Kenny Milne and injured Karl Dodd.
Falkirk did enjoy the best of the early possession, but it was Kilmarnock who carved out the first chance when Peter Leven's free-kick was nodded wide by Nish.
The hosts replied when new-boy Dean Holden ghosted in at the front post to direct a Russell Latapy corner into Alan Combe's arms.
On a blustery day, both sides sought to keep the ball on the ground as they probed for a decisive opening.
It almost came in the 11th minute when a flowing Falkirk passing move saw Tam Scobbie's angled left-footed drive turned round by Combe at his near post.
The home side had been more positive, but they were shocked when the visitors grabbed the opener.
Holden, handed his first start, carelessly gave the ball away to Naismith at a free-kick on the right and the youngster surged on a diagonal run across the pitch.
Nish made a neat run inside and Naismith's pass was perfect for him to drive a low left-footed shot past Kasper Schmeichel.
Kilmarnock suddenly had their tails up and Rocco Quinn, on loan from Celtic, was unlucky to see a net-bound 12-yard shot blocked.
But the second goal was only delayed until the 28th minute.
Quinn's corner caught Schmeichel exposed and Simon Ford's eight-yard header hit the underside of the bar before Naismith lashed home the rebound from close range.
Stunned Falkirk sought to regroup and Alan Gow should have done better than blaze a left-footed strike over.
Kilmarnock almost grabbed a third two minutes before the interval when a delightful attack saw Garry Hay's cross turned over the bar by Nish on the half-volley.
It almost got worse for the Bairns after 52 minutes, but Schmeichel came to their rescue when he pulled off a superb point-blank save from Naismith.
Three minutes later and the young Dane was again a hero when he blocked a drive from Nish.
The Ayrshire men were enjoying hitting on the break and Hay was next to threaten when his shot from the edge of the penalty area was deflected over.
Hughes had seen enough and Holden was sacrificed just before the hour to give Carl Finnigan, the 20-year-old striker signed from Newcastle earlier this week, his debut.
The game had gone flat and increasingly scrappy as Kilmarnock protected their lead in composed style.
Latapy saw a left-footed effort fly wide after 69 minutes but it was struck more in hope than expectation.
Latapy and Gow continued to probe without success as the home fans drifted away well before the finish.