Jean-Charles Castelletto scored first for Cameroon but Serbia led 3-1 after goals from Strahinja Pavlovic, Sergej Milinkovic-Savic and Aleksandar Mitrovic.
Cameroon and Serbia played out a 3-3 draw on Monday at the ongoing World Cup.
Cameroon fought back from two goals down to earn a point, keeping both teams in contention for a place in the last 16.
Jean-Charles Castelletto scored first for Cameroon but Serbia led 3-1 after goals from Strahinja Pavlovic, Sergej Milinkovic-Savic and Aleksandar Mitrovic.
Vincent Aboubakar and Eric Maxim Choupo-Moting then struck as Cameroon and Serbia both picked up their first point in Group G ahead of the later game between Brazil and Switzerland.