Some scholars have suggested that a negative consequence of strengthening child support enforcement is to encourage fathers to shift from regular sector to underground employment. We employ data from the Fragile Families and Child Wellbeing Study to investigate the relationship between the strength of child support enforcement (CSE) and levels of underground and regular sector employment among unmarried fathers. We find that, in general, living in a city with stricter CSE is associated with fewer hours of underground employment. We find little evidence that stronger enforcement is associated with employment or hours in the regular sector. (Contains 4 tables and 17 footnotes.)