Increasing support for same-sex marriage (SSM) is often explained as a consequence of rising tolerance of homosexuality across successive generations. This article argues that higher levels of SSM support among young people is also linked to their own emerging plans for couple and family formation. Panel data from 1,836 young Australians participating in the Social Futures and Life Pathways Project was used to analyze change in SSM attitudes between late adolescence (2008, aged 14/15 years) and early adulthood (2013, aged 19/20 years). During this period, the sample became less religious, more expectant of unmarried cohabitation, and more approving of SSM. Being male, living in outside a major city, not living with both biological parents, and being more religious were all associated with lower SSM support. Young people’s views on this issue developed in ways that were indicative of distinct (i.e., traditional vs. pragmatic) orientations toward intimate relationships formed earlier in adolescence.