Moussa Sow put Senegal ahead before Iheanacho won and then despatched the spot-kick to level the scores.
The goal was his fifth in six international appearances, to add to the seven he has scored for City in the 2016/17 campaign.
Elsewhere, three City players were involved in a crunch World Cup qualifier down in Buenos Aires as Argentina defeated Chile 1-0.
Lionel Messi put a decisive penalty past City keeper Claudio Bravo in the 16th minute to secure the win.
The result lifts Argentina to third in their qualifying group.
Finally Brazil cemented their place at the top of the group with a 4-1 win over Uruguay, with Fernandinho coming on after 82 minutes.