BACKGROUND: The relationship between perinatal psychiatric disorders and the use of effective contraceptive methods among postpartum women served by primary care clinics has not been established. STUDY DESIGN: This was a prospective cohort study with 831 pregnant women recruited from 10 primary care clinics of the public sector in S„o Paulo followed up to 18 months after delivery. RESULTS: Among 701 postpartum women, 644 women (91.8%) had resumed sexual activity. Two hundred fifty-three women (39.2%) were classified as using a less effective contraception method (LECM). The presence of perinatal psychiatric disorder (in pregnancy and/or postpartum) was not associated with LECM. Resumption of sexual life 3 months or beyond after delivery was associated with LECM (odds ratio=1.28, 95% confidence interval: 1.02-1.56). DISCUSSION: Although the use of an LECM after delivery is common, contraception choice is not associated with perinatal depressive/anxiety symptoms. However, women who delay the resumption of sexual activity after delivery should be counseled on the use of available contraceptive methods.