The Manchester United goalkeeper was starting in goal for his country who got off to a poor start when former Watford man Ismaila Sarr gave Senegal the lead.
With Cameroon chasing the game, Onana's team won a free-kick midway through the second, a crucial opportunity to try and get back into the game.
Placing the ball 35 yards from goal, Pathe Ciss was stood over the ball when the eccentric goalkeeper popped up behind him with a word of wisdom ahead of the set piece.
Onana clearly had something important to tell him after running nearly the entire length of the pitch, however his advice clearly didn't pay off as Ciss's free-kick drifted straight out of play for a goal kick.
Things got even worse for Cameroon when they went 2-0 down thanks to Habib Diallo's goal, before Jean-Charles Castelletto clawed one back seven minutes from time.
READ MORE ON ANDRE ONANA
Former Liverpool star steps in to calm down Andre Onana after AFCON axe
Onana doesn't feature in Cameroon AFCON opener after plane forced to land 150 miles away
However the game was killed off once-and-for-all in injury time as ex-Liverpool star Sadio Mane popped up with a goal to secure a crucial 3-1 win for Senegal.
That defeat means that Onana and Cameroon have just one point from their opening two matches, meaning that they now face a crucial deciding clash against Gambia on Tuesday.
Onana missed Cameroon's AFCON opener after a journey from hell saw his flight land 100 miles away from his teammates.
This came after leaving immediately after Man United's 2-2 draw with Tottenham.