It looked for so long as if Killie would miss out on Europe as the game trundled on goal-less with little hint of an opening. But Hearts' victory at Tynecastle was rendered meaningless by Mahood's toe-poke which left the Rugby Park faithful jubilant.
The first half was a fairly insipid affair, with no great urgency on display from either side. It was a full 18 minutes before Gordon Marshall in the Killie goal was called upon to make a save - Healy's free kick was reasonably comfortably dealt with by the keeper.
Celtic's pacy young strikers had a chance apiece within minutes of each other - first Jamie Smith beat the offside trap before shooting wide and then Shaun Maloney sped through the middle only to slice his shot.
Kilmarnock came within inches of opening the scoring in 33 minutes when Paul di Giacomo squared the ball to Jesus Sanjuan. Under pressure from Stephane Mahe, the Spaniard curled a shot against the post with Robert Douglas beaten. McCoist then spurned a gilt-edged opportunity to break the deadlock when he found space in the box, only to drag his shot harmlessly wide of goal.
At the other end, Gordon Marshall saved bravely at the feet of Tebily after the defender earned the break of the ball in the Killie area.
Prior to the goal, the most noteable incident came five minutes into the second period when Ally McCoist took his final bow on the professional football stage when he was replaced by Cristophe Cocard as Killie looked for goals. But it was Celtic who next went close to scoring when Shaun Maloney fashioned an opening for Stephane Mahe, but the Frenchman blazed wide from the corner of the box.
A 30-minute period of frustration ensued, with Kilmarnock looking increasingly desperate to break the stalemate with news filtering through from Tynecastle that Hearts were leading. But relief broke out round three-quarters of Rugby Park on 78 minutes when Mahood prodded home the opening goal. Di Giacomo beat Olivier Tebily for pace on the right and Mahood just got his toe to the cross before Ramon Vega to give the home side the lead.
Shaun Maloney ought to have equalised minutes later, but he connected poorly from eight yards out and sent the ball wide.
Kilmarnock: Marshall, McGowne, Innes, Dindeleux, MacPherson, Mahood, Sanjuan, Calderon, Hay, McCoist (Cocard 50), Di Giacomo.
Subs:- Meldrum, Reilly, Fowler, Boyd.
Goal:- Mahood 78.
Ref:- J Underhill.