An adapted version of Lamb's model was used to examine types of paternal involvement (positive engagement, access to the child, and financial stability) engaged in by cohabiting and non-cohabiting low-income fathers across four age groups. The sample consisted of 2,512 low-income fathers who participated in the Fragile Families and Child Well-being study. Univariate and multivariate analyses revealed that age group of father and cohabitation status had a significant effect on all three dimensions of paternal involvement. Adolescent fathers had more limited access and were less engaged than fathers in other age groups, even though they were more financially stable. This study provides practitioners with a developmental perspective on paternal involvement that is useful in working with low-income fathers.