This study was designed to test the relationship between perceived social impact, social worth, supervisor‐rated job performance (1 month later), and mediating effects by commitment to customers and work engagement. The hypotheses were tested with structural equation modeling analysis in a field study with 370 customer‐service employees from bank, retail, and sales positions. Results confirm that perceived social impact is associated with better job performance and that this relationship is mediated by work engagement. Furthermore, results support a second mediating mechanism in which perceived social impact and social worth are associated with engagement through affective commitment to customers. Finally, it was found that engaged employees are rated as better performers by supervisors 1 month later. This study supports the motivational approach to performance and highlights the role that interactions with customers may play in motivating service employees. Practical implications are discussed by highlighting the need to consider the social dynamics in service contexts. Copyright © 2015 John Wiley & Sons, Ltd.