We report an experience sampling study examining the within-individual effects of workplace interpersonal interaction characteristics on affect at work and daily well-being. A sample of 60 full-time employees completed measures of interpersonal interaction characteristics and affective states during each of 10 workdays and a measure of job satisfaction at the end of each workday. Overall, the employees provided 380 day-level data points. Hierarchical linear modeling (HLM) results indicated that interpersonal interaction characteristics were associated with affective states and job satisfaction. Furthermore, the effects of workplace interpersonal interactions on job satisfaction were mediated by affective states. Finally, positive affect mitigated the detrimental association between negative affect and job satisfaction. Copyright © 2010 John Wiley & Sons, Ltd.