Background Fear of childbirth (FoB) and depressive symptoms (DS) are experienced by many women and can negatively affect women during and after pregnancy. This study assessed patterns of FoB and DS over time and associations of postpartum FoB and DS with sociodemographic and obstetric characteristics. Methods We conducted a longitudinal study at six health facilities in Tanzania in 2018-2019. Pregnant women were consecutively assessed for FoB and DS before and after childbirth using the Wijma Delivery Expectancy/Experience Questionnaire versions A & B and the Edinburgh antenatal and postnatal depressive scale. This paper is based on 625 women who completed participation. Results The prevalence rates of FoB and DS during pregnancy were 16% and 18.2%, respectively, and after childbirth, 13.9% and 8.5%. Some had FoB (6.4%) and DS (4.3%) at both timepoints. FoB was strongly associated with DS at both timepoints (p < 0.001). Both FoB (p = 0.246) and DS (p < 0.001) decreased after childbirth. Never having experienced obstetric complications decreased the odds of postpartum and persisting FoB (adjusted odds ratio (aOR) 0.44, 95% confidence interval (CI) 0.23-0.83). Giving birth by caesarean section (aOR 2.01, 95% CI 1.11-3.65) and having more than 12 hours pass between admission and childbirth increased the odds of postpartum FoB (aOR 2.07, 95% CI 1.03-4.16). Postpartum DS was more common in women with an ill child/stillbirth/early neonatal death (aOR 4.78, 95% CI 2.29-9.95). Persisting DS was more common in single (aOR 2.59, 95% CI 1.02-6.59) and women without social support from parents (aOR 0.28, 95% 0.11-0.69). Conclusions FoB and DS coexist and decrease over time. Identifying predictors of both conditions will aid in recognising women at risk and planning for prevention and treatment. Screening for FoB and DS before and after childbirth and offering psychological support should be considered part of routine antenatal and postnatal care. Furthermore, supporting women with previous obstetric complications is crucial. Using interviews instead of a self-administered approach might have contributed to social desirability. Also, excluding women with previous caesarean sections could underestimate FoB and DS prevalence rates.