Cleveland Movie Blog writes:
The script isn’t as smart as writers Etan Cohen, David Koepp, and Jeff Nathanson might think. Sure, MIB III toys with the conundrums intrinsic to temporally-affected actioners (TIMECOP, STAR TREK IV, TERMINATOR, etc.) milking several what-if moments for desired effect and bouncing them off MIB’s now-familiar ray gun technology (the penlight neuralyzers used to wipe the memories of witnesses are lambasted). The screenplay is more successful spelunking Sixties’ hippie culture and racial tension: Agent J hesitantly salutes a Black Panther and berates a pair of dumb-and-dumber traffic cops for profiling him, only to have his civics lesson back-fire. But the clever, lump-in-the-throat denouement ties the series up nicely. With a big black bow.