A father’s mental health is important for family well-being, but research is scarce on paternal symptoms during the transition to fatherhood. This study identified fathers’ latent mental health trajectory classes from the pre- to postnatal period and examined their associations with early fathering experiences. It further analysed, whether a family’s infertility history was associated with mental health trajectory classes and moderated their effects on fathering experiences. Finnish fathers (N = 773) reported psychological distress (General Health Questionnaire; GHQ-36) and depressive symptoms (Beck Depression Inventory; BDI-13) in pregnancy (T1), and at 2 months (T2) and 12 months (T3) postpartum. They further reported their fathering experience (Parenting Stress Index; PSI-36) at T2 and T3. Results revealed five paternal mental health trajectory classes, differing in timing and course of symptoms across the pre- and postpartum: stable low (79%) and moderate increasing (9%) levels of symptoms, and prenatal (5%), early fatherhood (3%) and heterogeneous high levels of (4%) problems. The trajectory classes were associated with fathering experiences within parental, interactive and child domains, across the child’s first year. The stable low levels of symptoms-class showed the most positive experiences and the heterogeneous high levels of problems-class the most negative ones; mental health problems in the early fatherhood-class reported negative fathering experience, but only when the child was 2 months old. A family’s infertility history neither showed any significant association with trajectory classes nor moderated their impact on early fathering, supporting the growing evidence that infertility treatments do not place an additional burden on early fatherhood.