Objectives: This study aimed to identify the relationship between antenatal depression and pregnancy outcomes, including the risk of developing postpartum depression in Oman. Methods: This follow-up prospective longitudinal cohort study included pregnant women attending primary healthcare institutions in Muscat, Oman from January to November 2014. The Edinburgh Postnatal Depression Scale (EPDS) was used to screen for antenatal and postnatal depression. Pregnant Omani women with a gestational age ≥32 weeks attending 12 local health centres for antenatal care in Muscat were invited to participate. Recruited women were followed-up at 6–8 weeks after delivery. The following pregnancy outcomes were assessed: mode of delivery (normal or Caesarean section [CS]), gestational age at delivery (preterm or fullterm), baby’s birth weight and development of postnatal depression. Results: A total of 959 women participated in this study (response rate: 97.3%). In total, 233 women (24.4%) had antenatal depression with a score of ≥13 on the EPDS. Of the 592 participants (61.7%) who attended postnatal clinics at 6–8 weeks post-delivery, 126 (21.3%) were positive for postnatal depression. Logistic multivariate regression analysis showed that antenatal depression was associated with increased risk of CS (odds ratio [OR] = 1.79; 95% confidence interval [CI]: 1.20–2.66) and postnatal depression (OR = 8.63; 95% CI: 5.56–13.39). Conclusion: Screening women for antenatal depression and providing appropriate management may reduce adverse pregnancy outcomes and the risk of developing postnatal depression.Keywords: Depression; Postnatal depression; Women Health Services; Maternal Health Services; Pregnancy; Primary Health Care; Oman.