In the face of growing diversity in marital and cohabiting relation-ships, the impact of romantic partnerships on criminal desistancemay likewise have grown complex. This study investigates howpremarital cohabitation and serial cohabitation might influencecriminal behavior. We also examine the role of gender in thedesistance process. Using data from the National LongitudinalStudy of Adolescent to Adult Health, we find that married menwho cohabited with the spouse before marriage tended to com-mit more crimes than those who did not, whereas among marriedwomen premarital cohabitation was not associated with anincrease in crime. In contrast, serial cohabitation’s effect did notvary by gender—male and female serial cohabitors both commit-ted more crimes than one-time cohabitors. We conduct analysesto address selection and the findings are robust. Our work sug-gests that exploring heterogeneity within changing patterns ofmarriage and cohabitation is critical to understanding desistance from crime.