Background <p>Strengthening professional identity is crucial to mitigate nursing students’ attrition and ensure a sustainable workforce. While the hidden curriculum and learning engagement are believed to influence this identity, their interrelationships remain unclear.</p> Aims <p>This study aims to explore the relationship between hidden curriculum and professional identity and examine whether learning engagement mediates the relationship between hidden curriculum and professional identity.</p> Methods <p>A cross-sectional study was conducted among 623 undergraduate nursing students from two medical colleges in China. The general information questionnaire, Hidden Curriculum Evaluation Scale in Nursing Education, Utrecht Work Engagement Scale-Student, and Professional Identity Scale for Nursing Students were used for data collection, and IBM SPSS 26.0 and PROCESS macro (Model 4) were used for statistical analysis.</p> Results <p>Hidden curriculum, learning engagement, and professional identity were significantly positively correlated. Learning engagement partially mediated the relationship between hidden curriculum and professional identity, accounting for 44.13% of the total effect.</p> Conclusions <p>Nursing educators should proactively develop the hidden curriculum and implement strategies to boost learning engagement, thereby fostering students’ professional identity and reducing future workforce attrition.</p>