But the second-seeded Nadal was challenged by the 24th-seeded Thomaz Bellucci of Brazil, losing his serve four times before winning 6-2, 7-5, 6-4.
Nadal is attempting to become the second man to win five French Open titles. Bjorn Borg holds the record of six.
Nadal won his first 31 career matches at Roland Garros before losing to Robin Soderling in the fourth round last year. He's now 35-1 at the clay-court Grand Slam tournament.