This paper examines how family-supportive supervisor behaviours (FSSBs) are associated with employees’ in-role job performance and perceived promotability, and how prosocial motivation moderates these associations. Drawing on the norm of reciprocity from social exchange theory; we propose that FSSBs are positively associated with employees' in-role job performance and perceived promotability. Furthermore, building on the Work–Home Resources model (W-HR model), we propose that family performance of employees may be a mediator between FSSBs and employees' work outcomes. Expanding our model, we integrate an individual difference, prosocial motivation and propose that prosocial motivation may influence the associations between FSSBs and employee outcomes via family performance in such a way that the indirect effect of family performance is negative for subordinates with high prosocial motivation and this indirect effect is positive for employees with low prosocial motivation. Using matched dataset of 187 supervisor–subordinate dyads across four organizations located in Chile, Argentina and the Philippines; our findings from multi-level analyses reveal a direct positive association between FSSBs and in-role job performance and perceived promotability. However, family performance did not mediate the associations between FSSBs and employees' outcomes. Interestingly, our results revealed that for subordinates characterized by high (vs. low) prosocial motivation, the mediation of family performance between FSSBs and work outcomes weakens (vs. strengthens). Our focus on prosocial motivation also underlines the dark side of showing concern for others.