This paper presents a study linking knowledge workers' perceptions of a commitment-based human resource (HR) system to their role behaviors by adopting psychological contracts as a linking mechanism. The hypotheses are tested by matching and analyzing data collected from knowledge workers in Taiwan's high-tech firms. The results indicated that knowledge workers' perceptions of a commitment-based HR system improve their in-role and extra-role behaviors via shaping their relational psychological contracts. In addition, our study also demonstrated that knowledge worker perceptions of a commitment-based HR system were negatively associated with their transactional psychological contracts. These findings have implications for research on human resource management and psychological contracts as well as for managers seeking to enhance or maintain a firm's competitive advantages.