Ribery set up Etienne Capoue for the opener before wrapping the victory up with a fine chip 10 minutes from time in a one-sided encounter that came to life after the interval.
Christophe Jallet scored France's second goal before Belarus reduced the arrears through Anton Putilo 18 minutes from time.
Les Bleus snatched their second win in two games four days after a 1-0 victory in Finland but they lacked inspiration and Didier Deschamps's side were lucky not to trail the visitors early in the second half.
They will need to improve dramatically to stand a chance against world and European champions Spain in their qualifier in Madrid next month.
"Look at Spain, they struggled to beat Georgia," Deschamps told reporters, referring to Spain's last-gasp 1-0 win in Georgia earlier on Tuesday.
"The most important thing is to win matches. We have six points, we could not have more from these two games. It's now up to the players to stay as good as they are by playing well in their clubs until next time.
"Spain remain the favourites in this group, but it's good for us that we travel there with already six points in the bag."
Deschamps had decided to give Karim Benzema a hand up front by playing Olivier Giroud but it did not seem to help Les Bleus who produced a lacklustre display in the first half.
The hosts had their best chance after 13 minutes when a Giroud header from Ribery's cross was parried away by Sergei Veremko with a fine dive to his right.
Veremko denied Mamadou Sakho eight minutes from the interval when he stopped the defender's downward header on his goal-line.
Belarus had their first chance in the 47th minute but it took a lightning quick Hugo Lloris save to deny Stanislav Dragun from close range.
It spurred France into action.
Two minutes later, Ribery broke down the right flank and Capoue, who started in place of the injured Abou Diaby, connected with the winger's pass to beat Veremko with a low shot from just inside the box.
Jallet doubled the tally 19 minutes later when what seemed to be an attempted cross dropped in under the bar.
Belarus pulled one back in the 72nd when Putilo netted from close range after Lloris had saved Sergei Kornilenko's penalty.
Ribery, however, put the result beyond doubt when he chipped the ball past Veremko 10 minutes from time.
France's next game is a home friendly against Japan on October 12.
