Married men earn more than unmarried men. Previous research suggests that marriage itself “causes” some of the difference, but includes few men who fathered children out of wedlock. This paper asks whether increasing marriage (and possibly cohabitation) following a non-marital birth is likely to increase fathers' earnings and labor supply. The analyses are based on a new birth cohort study – the Fragile Families and Child Wellbeing Study – which follows unmarried parents for the first five years after their child's birth. Results provide some support for the idea that increasing marriage will lead to increased fathers' earnings.