Salesperson humor usage (SPHU) is often linked with positive outcomes, but little is known about its potential negative effects on salespeople. This study uses ego depletion theory to investigate the negative spillover effect of daily SPHU on work–family conflict via experience sampling method, using data from 109 salespeople over 10 workdays. Results show that daily SPHU is positively associated with daily work–family conflict through increased daily ego depletion. Moreover, the study examines daily supervisor developmental feedback as a context‐relevant moderator that can alleviate the relationship between daily SPHU and ego depletion. By detailing the mediating and moderating mechanisms of daily SPHU spill‐over in a sales interaction context, this study not only supports the perspective of ego depletion in understanding the dark sides of daily SPHU but also offers insights for organizations to inhibit its negative effects.