We know little about population-based patterns on same-sex partnership and health from a longitudinal perspective, largely due to data limitations. In this study, we analyzed nationally representative longitudinal data to compare changes in self-rated health trajectories for individuals in same-sex cohabitation, different-sex marriage, and different-sex cohabitation. Data were drawn from the 1996, 2001, 2004, and 2008 panels of the Survey of Income and Program Participation, with each panel including 2–4 years of follow-up information on self-rated health. The analytic sample included 103,995 respondents who contributed 294,944 person-period records. Results from growth curve models suggest that same-sex cohabitors experienced a slower rate of decline in self-rated health over time than both different-sex married and different-sex cohabiting respondents. Further analyses show that same-sex cohabitation is associated with a slower rate of health decline only for women but not for men. We discuss the implications of these findings in relation to the minority stress theory and the gender-as-relational perspective.