Although the empirical links between marriage and desistance are well established, very little is known about the degree to which cohabitation is associated with changes in criminal behavior. This is a significant oversight given that, among some segments of the population, cohabitation has become more common than marriage. In this article, the author investigated the links between cohabitation and desistance from crime. In doing so, particular attention was paid to the possibility that similarities between the apparent effects of marriage and cohabitation are obscured by variations in relationship quality and the increasing tendency for cohabitation to precede marriage. Analyses based on the National Longitudinal Survey of Youth 1997 (N = 3,232) indicate that cohabitation is associated with reductions in the rate of property and drug offending, but not the termination of violent, property, or drug offending. By contrast, marriage is consistently associated with large reductions in the rate of offending across the 3 crime categories as well as the abandonment of those crimes. These results provide greater insight into the links between adult family relationships, such as cohabitation and marriage, and desistance from crime.