The 145-pound title bout was supposed to headline the pay-per-view event, which takes place at Staples Center in Los Angeles. No replacement has been announced.
UFC officials confirmed Aldo's injury to ESPN.com. The news was first announced on Wednesday's edition of UFC Tonight.
Aldo (24-1) defended the UFC title for the sixth time in a unanimous decision over Ricardo Lamas in February. The 27-year-old has already defeated Mendes once, via first-round knockout at UFC 142 in January 2012.
Mendes (16-1) has won five consecutive fights, including four knockouts, since that loss. He has yet to compete in 2014. His most recent win came via decision against Nik Lentz at a UFC on Fox card in December.