Capriati beat Russian Alina Jidkova 7-6 (7-3), 7-5 in a rain-delayed affair, while Pierce defeated Aussie Nicole Pratt 6-1, 6-1. The Capriati-Jidkova match was interrupted by rain for 2 hours, 39 minutes.
Capriati and Pierce will square off in the third round this week.
Capriati captured this event -- the former Canadian Open -- as a 15-year-old way back in 1991.
Fifteenth-seeded American Chanda Rubin posted a first-round victory over German Antonia Matic 6-4, 6-3.