<p>This study aims to comprehensively examine the impact of internships on the employability of professional Master’s degree students in China and the potential mechanisms underlying this impact. Based on survey data from 2231 students at Chinese universities, the study distinguishes employability into subjective employability, which refers to perceived employability measured by job-seeking ability and sustained employment, and objective employability, which refers to the number of job opportunities. Internships were assessed through two approaches: duration of internship experiences and authenticity of internships, with the latter expressed in terms of cognitive authenticity and environmental authenticity. The results show that internships positively influence both subjective and objective employability. Furthermore, internship duration significantly predicts all employability outcomes, while cognitive authenticity is positively associated with perceived and objective employability. Environmental authenticity is linked to perceived employability. The study also identifies the mediating roles of reflective learning and social relationship development in the link between internship experiences and employability outcomes. These processes reflect how internships contribute to the accumulation of cultural and social capital, which are key drivers of employability. Furthermore, heterogeneous effects are observed across different levels of student employability. After correcting for sample selection bias, internships remain robust predictors of employability. These findings highlight the developmental patterns of employability among professional Master’s degree students and support the policy recommendation of embedding high-quality, authentic internships within university-industry cooperation programs that emphasize reflective learning and social capital formation.</p>