Both mothers and fathers are at risk for experiencing postpartum depressive symptoms shortly after the birth of a child. Previous studies suggest mothers' and fathers' depressive symptoms to be interrelated. This study examined bidirectional relations between mothers' and fathers' depressive symptoms across four years postpartum. Longitudinal data for this study were collected across five waves from 485 mothers and 359 fathers of infants when infants were on average 6 months-old until children were 54 months-old (1-year lags). Mothers and fathers reported on their depressive symptoms using the Center for the Epidemiological Studies Short Depression Scale (CES-D 10). A random intercept cross-lagged panel model (RICLPM) was specified to examine the bidirectional relations between mothers' and fathers' depressive symptoms over time. At the between-person level, mothers' and fathers' depressive symptoms were positively associated. At the within-person level, unique carry-over effects were found for mothers and fathers in that when reporting higher depressive symptoms than their trait levels, they were more likely to report higher depressive symptoms one year later. Moreover, intermittent cross-lagged effects were observed from mothers' depressive symptoms to fathers' depressive symptoms during toddlerhood. The sample was not racially or structurally diverse thereby limiting the generalizations of the findings. After the birth of a child, mothers and fathers are at risk for experiencing chronic depressive symptoms which can have implications for individual, couple and child health. Mothers' depressive symptoms are related to fathers' depressive symptoms over time. •Mothers' and fathers' depressive symptoms are related across the first four years postpartum.•Carry-over effects were observed for both mothers and fathers.•Intermittent spillover effects were observed from mothers' depressive symptoms to fathers' depressive symptoms one-year later.