Background Despite growing interest in men's perinatal mental health, we still know little about whether becoming a new father is associated with increases in psychological distress. Aims To use prospective longitudinal data to investigate whether becoming a first-time expectant (partner pregnant) and/or new father (child 51 year) is associated with increases in depression and anxiety. Method Men were aged 20-24 years at baseline (n = 1162). Levels of depression and anxiety were measured at four time points over 12 years. Over this time, 88 men were expectant fathers, 108 men were new fathers and 626 men remained non-fathers. Results Longitudinal mixed models showed no significant increase in depression or anxiety as a function of expectant or new fatherhood, as compared with pre-fatherhood levels. Conclusions Our findings suggest that, generally, expectant and new fathers are not at greater risk of depression or anxiety. Future epidemiological research should continue to identify men who are most (and least) at risk to focus resources and assistance most effectively.