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.
Chamberlain Oguchi went 8 for 14 from 3-point range to finish with 35 points for Nigeria.