Manchester City strengthen their hold on second place in the Premier League.
Substitute Gabriel Jesus's late goal gave them lead.
Jesus found the net in the 80th minute after an assist from Riyad Mahrez.
Kasper Schmeichel, who saved Aguero's penalty earlier (62), couldn't save this one and let it slip past him.
In the battle of third versus second, Jamie Vardy hit the post for Leicester early on after being put through one-on-one in a goalless opening period, before Aguero's penalty miss following a Dennis Praet handball, and Jesus' eventual winner.
The result means second-placed Manchester City are now seven points ahead of Leicester.
