The Celts dominated possession early on, controlling nearly 80% of the ball in the opening 20 minutes, but Kilmarnock’s deep defensive setup limited clear goal-scoring opportunities.
Making his debut for Celtic, Sebastian Tounekti looked lively on the left wing, threatening with a clever run and a near-lob over the goalkeeper, before threading a pass to Benjamin Nygren, whose shot narrowly missed the target.
Iheanacho entered the fray with 20 minutes remaining, replacing Daizen Maeda, and added fresh energy to the attack.
Kilmarnock drew level from a corner with David Watson’s header, but Celtic’s persistence paid off in the dying moments.
A VAR-awarded penalty saw Iheanacho calmly slot the ball high into the net, securing a thrilling 2-1 win and keeping Celtic’s unbeaten Premiership start intact.