Understanding how leaders can promote proactive employees’ prosocial motivation and encourage them to contribute to the organization in the form of taking charge is theoretically and practically important. By integrating trait activation theory and proactive motivation model, we propose servant leadership as a crucial work context enhancing proactive employees’ prosocial motivation, which in turn prompts their engagement in taking charge. Three-wave data collected from retail employees and their store managers in Hong Kong, China supported our hypotheses. We find that prosocial motivation is a key mediating mechanism underlying the positive relationship between proactive personality and taking charge. The presence of servant leadership makes this indirect effect stronger. This research enriches extant taking charge and proactivity literature. It also brings important implications for organizations to capitalize on proactive employees.