Purpose The purpose of this paper is to investigate the moderating roles of trust in leaders and felt trust by leaders on the relationship between proactive personality and voice behaviour. Design/methodology/approach Self-report data were collected from 242 employees in China using an online survey. Findings Trust strengthens, whereas felt trust weakens the relationship between proactive personality and voice behaviour. Proactive personality is related to voice behaviour more positively when trust in leaders is high or when felt trust by leaders is low. Practical implications Trust in leaders and felt trust by leaders provide different motivational cues for employee proactivity. It would be wise for leaders to develop different trusting relationships with employees who have different levels of proactive personality. If leaders expect to promote voice behaviour in the workplace, they should gain trust from proactive employees by demonstrating their own trustworthiness while signalling or granting trust to less proactive employees by engaging in trusting behaviours. Originality/value The present research extends the boundary conditions of the effectiveness of proactive personality by demonstrating that proactive employees' motivation to speak up can be enhanced or substituted by relational variables. The authors thus underscore the importance of the personality x relations perspective when examining employee proactivity. In addition, the authors contribute to the trust literature by advancing the understanding of different roles of trust and felt trust in influencing proactive motivation in social interactions.