France will finish no worse than third in Group A.
Batum nailed a 3-pointer to put France up 65-62 and the French (4-1) never trailed again after Nigeria had battled back from an 11-point halftime deficit.
The Portland Trail Blazers standout hit two more 3s down the stretch. His 3-pointer with 2:38 to play gave France a 75-68 lead and he drained another for a 79-70 advantage. Batum also had six rebounds.
Boris Diaw, who plays for the San Antonio Spurs, scored 10 points for France. Spurs guard Tony Parker had seven assists in 21 minutes for France.
Chamberlain Oguchi went 8 for 14 from 3-point range to finish with 35 points for Nigeria.