Young adulthood, a time of major life transitions and risk of poor mental health, may affect emotional well-being throughout adult life. This article uses longitudinal survey data to examine young Australian women's transitions across 4 domains: residential independence, relationships, work and study, and motherhood. Changes over 3 years in health-related quality of life, optimism, depressive symptoms, stress, and life satisfaction, were examined in relation to these transitions among 7,619 young adult participants in the nationally representative Australian Longitudinal Study on Women's Health. Positive changes in mental health occurred for women moving into cohabitation and marriage, whereas reductions were observed among those experiencing marital separation or divorce and those taking on or remaining in traditionally "feminine" roles (out of the workforce, motherhood). The data suggest that women cope well with major life changes at this life stage, but reductions in psychological well-being are associated with some transitions. The findings suggest that preventive interventions to improve women's resilience and coping might target women undergoing these transitions and that social structures may not be providing sufficient support for women making traditional life choices.