BACKGROUND: Depression in fathers in the postnatal period is associated with an increased risk of some adverse child developmental outcomes. One possible mechanism for the familial transmission of risk is through the negative effects of depression on parenting and the parent-child relationship. So far, evidence indicates that depressed fathers tend to be more withdrawn in their early interactions. However, the interaction dimensions studied to date may not be able to detect and accurately classify unique features of father-infant play - including physically stimulating and highly rousing episodes of play. Hence, in this matched design comparison study, we set out to examine, for the first time, links between diagnosed paternal depression in the postnatal period and playfulness in father-infant interactions. METHODS: Fathers and their infants were assessed when the infants were 3 months old. Paternal depression was diagnosed using a structured psychiatric interview. Currently depressed (n = 19) and non-depressed (n = 19) fathers were individually matched on age and education. Fathers were filmed playing with their children. Four dimensions were coded for paternal playfulness during free-play: physicality, playful excitation, tactile stimulation and active engagement. RESULTS: Depressed fathers, compared to non-depressed fathers, engaged in fewer episodes of playful excitation (mean scores: 0.71 vs.2.53, p = 0.005), less gentle touch (mean time: 38.57 vs. 53.37, p = 0.015) and less active engagement (mean scores: 2.29 vs 3.24, p = 0.044). When controlling for infant fretfulness, the findings remained largely unchanged. LIMITATIONS: The sample size was small and the sample was limited to mostly white, well-educated fathers. CONCLUSIONS: Playful paternal behaviours as early as 3 months differ between fathers with and without depression. These changes may help in understanding children's risk in relation to paternal psychopathology and could be a target for future family interventions.