Both sides started the game brightly forcing early corners bur neither was able to fashion a clear-cut opening. A typical dancing run from Ethan Ross saw the Dons skipper wriggle clear of his full-back but unfortunately his cut-back couldn't find a man in red.
Archie Mair was called into action after 10 minutes when a good cross from the left from Josh Walker was hit on the volley by Monk, but the keeper made a comfortable save.
Five minutes later, a well-worked corner routine between Connor Barron and Dean Campbell saw the latter fire a fierce left-foot shot towards the Killie goal, but it was deflected away to safety.
Aberdeen broke the deadlock on 16 minutes when a fine, flowing passing move through midfield saw the ball played into the path of Ethan Ross and the skipper made no mistake from eight yards. The first really good move of the match getting its just rewards.
Kieran Shanks thought he'd made it 2-0 on 24 minutes when he latched on to a through ball from Mykyta to slot the ball into the net. His joy was short-lived though as the flag was up for offside.
Kyle Dalling really should have doubled the Dons advantage when Barron picked him out in the box, but the big defender headed wide. The home side were in control although Killie were defending resolutely.
Lewis Duncan was next to threaten Walker's goal when he fired just over just before the half hour. With eight minutes left of the half Taylor had a rare opportunity for the visitors, but his twenty-five yarder flew well over. That gave Killie a lift and Monk tried his luck at goal, but the ball curled past Mair's post.
Aberdeen raced back into attack and Duncan was unlucky to see his driven cross fly across the face of goal without anyone getting a finishing touch.
On 43 minutes Kilmarnock drew level, a fine Brindley cross being headed in at the far post by Monk. A goal slightly against the run of play but nevertheless well-created.
Aberdeen threatened again when Ross played Shanks in, the visitors defence throwing bodies on the line to defend their goal.
The Dons will have been disappointed to concede so close to the break after dominating long periods of the first period.
Half time - Aberdeen 1 Kilmarnock 1
Brindley again threatened the Aberdeen goal early in the second half, forcing a solid save from Mair. On 50 minutes Mair was forced to make a great block from Monk after a slipup by the Dons defence.
Monk again threatened on 55 minutes, a great piece of defending from Lloyd Robertson denying the Killie striker.
Aberdeen won a penalty on 57 minutes when Ross was bundled over by Shields and the Dons hitman made no mistake from the spot to give his side the lead again.
The Dons looked to have made it three on 64 minutes when Dalling fired a Barron corner into the net, but referee Mazzoni had spotted an infringement and the goal was chalked off.
Killie still looked dangerous when they went forward but they had keeper Walker to thank when he saved bravely at the feet of Ross. A third goal for the Dons would surely have sealed the victory.
Coach Scott Anderson made his first change on 74 minutes, Danny Strachan and Michael Dangana replacing Shanks and Hanratty.
Killie subs Ross Smith and Renicks combined on 79 minutes, the latter heading narrowly over. The game continued to be played at a high tempo but neither side was finding the telling pass in the final third. Renicks became the game's first booking with three minutes left after a clumsy challenge on Campbell.
On 90 minutes Ethan Ross was withdrawn with Mark McLauchlan coming on, the Dons two-goal hero having taken a knock. The Dons saw the remaining few minutes of the game out comfortably to seal a semi-final berth.