Introduction: No studies on paternal postnatal depression (PPND) have been performed in Poland. Aim: The aim of the study was to estimate the symptoms of depression in women and men and identify the determinants of mental health of fathers after the birth of their child. Material and methods: Parents (142) participated in the study during the period 1 to 12 months after the birth. Results and discussion: The analyses reveal that 13% of fathers and 18% of mothers after the birth of their child had Edinburgh postnatal depression scale (EPDS) scores of 10 or higher, which indicates possible depression. At score 12 and more, the proportion detected by EPDS decreased to 7% of fathers and 13% of mothers, which is an indicator of major depressive disorder. At EPDS score 12 and more, a probable depressive disorder was indicated in 10% of fathers in the period of 1–3 months, 7% of fathers at 4–7 months and 4% of fathers at 8–12 months. The symptoms of maternal depression at a score of 12 and more were detected in 16% of women at 1–3 months, 12% at 4–7 months 11% at 8–12 months. PPND was significantly associated with depression in mothers OR 5.7, lower education OR 4.3, low financial income OR 6.0, decreased relationship satisfaction OR 3.3, and previous history of depression OR 3.2. Conclusions: Psychosocial factors were strong predictors of PPND up to a year after the birth of the child. The authors suggest the routine screening and assessment of both parents should occur during the woman’s pregnancy and in the postnatal period.