Increasingly, employees are recognized as important enactors and contributors to corporate social responsibility (CSR) activities, making their engagement a critical consideration of internal stakeholder management. While the positive outcomes of employees’ CSR engagement have been extensively investigated, the present study focuses on an essential yet understudied question: How do employees engage in organizational CSR activities through communication efforts? We proposed and tested an employee-centered CSR engagement model based on the reasoned action approach. Findings from a survey with 406 employees indicated that CSR communication consisting of both instrumental and co-creational aspects could effectively foster employees’ cognitive, emotional, and behavioral engagement in CSR. Positive attitudes and perceived supportive workplace norms regarding CSR participation are key mediators. This study answers the call for more research on the individual-level drivers of CSR engagement from an employee perspective and offers practical implications for internal CSR communication design.