Most of the pressure was still being applied by Chile and they eventually cracked the defence of their opponents with substitute Alexis Sanchez clipping in a delightful cross for Vidal to head home.
Though Chile is participating in the confederations cup for the first time, Cameroon has been there thrice and even lose the 2003 final to France. Vargas scored in overtime but the goal was ruled out for offside after the use of the video assistant referee (VAR) technology.
South American champion Chile faces Cameroon on Sunday, before playing against Germany and Australia in its remaining group stage games.
However, it took more than a minute from the ball going into the net to the goal being overturned by the VAR and the game was not restarted before the interval.
Sanchez charged through the Chilean defense, but saw his shot saved by Ondoa, only for Vargas to score the rebound.
La Roja started like a house on fire as Vargas rattled the upright before Fabrice Ondoa denied Fuenzalida inside the opening five minutes.
However, clear chances were hard to come by until Vargas fired high and well over the bar after being played into a pocket of space in the 40th minute by Vidal.
When is Chile vs Cameroon and where can I watch it?
In the second period Cameroon were resigned to very few notable efforts with captain Benjamin Moukandjo firing his free-kick wide.
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