Hong Kong adolescents are at increased risk for poor psychological well-being. A higher quality relationship between adolescents and their mothers may promote positive adjustment, given the strong family-oriented culture in Hong Kong. Potential pathways by which the mother–adolescent relationship may facilitate better adolescent subjective well-being, however, remains unclear. Current resilience theories underscore the importance of examining the role of external resources for individual’s resilience capacity, and cascading effects of family functioning on adolescent subjective well-being outcomes by promoting their resilience resources. Therefore, we tested the hypothesis that a higher quality mother–adolescent relationship will be associated with better adolescent subjective well-being via improved resilience resources. Adolescents from Hong Kong (N = 133; M age = 11 years, SD = 0.21, 51.8% female) reported on their relationship with their mothers, resilience resources, and subjective well-being at Time 1 and one year later at Time 2. We used the half-longitudinal mediation model for testing mediation with two time points. Both resilience resources and mother–adolescent relationship quality were positively associated with adolescent subjective well-being, concurrently and one year later. Further, adolescents’ resilience resources mediated the association between mother–adolescent relationship quality and their subjective well-being one-year later. Our findings provide support for the cascading effect of external resources (i.e., mother–adolescent relationship quality) on adolescents’ resilience resources and their later subjective well-being. The findings can inform the improvement of existing resilience enhancement programs by adding components that strengthen family relationships.