Informed by role boundary congruence, person–environment fit, and conservation of resources theories, this study tested a cross-sectional, moderated-mediation model of work–study boundary congruence in working tertiary students (N = 401). In this model, contextual supports (family and workplace) were associated with well-being, academic performance, and employability, and these relationships were mediated by boundary congruence and were conditional on level of proactivity. The study found that family support (FS) was related to better well-being, academic performance, and employability, whereas workplace support was related to better academic performance. Boundary congruence mediated between FS and the three outcomes and also mediated between workplace support and academic performance. The mediated relationships were stronger when proactivity was lower. The study demonstrated that work–study boundary congruence is a potential mechanism for explaining the relationships between contextual supports and student outcomes and showed that these relationships were conditional on the person factor of proactivity.