The association between marital status and health among men has been well documented, but few studies track health trajectories following family structure transitions among unmarried fathers. Using the Fragile Families and Child Wellbeing Study this article examines trajectories of paternal mental health and self-rated health, focusing on transitions into and out of residential relationships with the child's biological mother or a new partner during a five-year post-birth period (N = 4,331). Continuously married fathers report higher time-specific self-rated health and fewer mental health problems than continuously single fathers, controlling for underlying health trajectories. The disparity, however does not increase over time, providing little support for the marital resource model during these years. Static group differences suggest that resources fathers carry with them into unions may buffer them from the negative effects of union dissolution. The implications of these findings for cohabitation, as well as selection and causation arguments, are also discussed.