The present study applied the theory of planned behavior (TPB) to unfold the social cognitive antecedents of acculturation and investigated the effects of acculturation on psychological distress using a longitudinal design. A total of 180 mainland Chinese university students studying in Hong Kong completed three sets of questionnaires every 2 months for a period of 6 months. Findings from structural equation modeling (CFI = 0.97, NNFI = 0.96, RMSEA = 0.05) confirmed the explanatory power of TPB on acculturation. The effect of acculturation on psychological distress was mediated by sociocultural adaptation and acculturative stress. The results highlight the importance of sociocultural adaptation in the course of acculturation and confirm acculturation as an identifier of risk rather than a direct predictor of psychological distress. Practical implications for university counseling centers in facilitating better cultural adjustment among students with a different cultural background are suggested. (Contains 2 tables and 2 figures.)