His impact was felt when the winger provided the cross from the left flank for Vidal to head home.
The defensive wall set up by the Indomitable Lions looked to have finally been broken when Vargas dinked the ball past Cameroon's goalkeeper after a nice through ball from Arturo Vidal in first half stoppage time.
Although replays appeared to show Vargas in a marginally offside position, concerns will be raised over the length of time it took to make the decision and the confusion surrounding the referee's signals to viewers on television.More news: Despite Clinton impeachment vote, Gingrich says President 'cannot obstruct justice'
Vargas followed up to notch Chile's second in the 90th minute and wrap up the points in Group B's opening match.
Cameroon was under pressure immediately, when Eduardo Vargas' first-minute shot cannoned off the post and rebounded back into goalkeeper Fabrice Ondoa, nearly going in.
It was all about the South Americans in the entire first half, but they missed a couple of chances.
Chile also has matches against Germany in Kazan next Thursday, and Australia on June 25 in the Russian capital.