Affect spin refers to shifts in emotional states over time; it captures people’s reactivity to affective events. Recent evidence suggests that affect spin has costs for both organizations and for employees, yet little is known about the antecedents of affect spin and possibilities to reduce it. The present study builds on existing research by examining mindfulness as an antecedent of affect spin in employees. Specifically, we hypothesized that mindfulness practice reduces affect spin over time. We also expected that levels of affect spin are positively related to emotional exhaustion and negatively to job satisfaction, both at the between- and the within-person level of analysis. Finally, we hypothesized that decreases in affect spin due to mindfulness practice are associated with lower levels of emotional exhaustion and higher levels of job satisfaction. To examine trajectories of affect spin over time, we tested our hypotheses in a randomized controlled mindfulness intervention study (with a wait-list control group; total N = 173 individuals) using experience sampling methods over the course of a month. Results revealed that mindfulness practice led to gradual decreases in affect spin over the course of the study. As expected, between-person differences in affect spin were positively related to emotional exhaustion and negatively to job satisfaction. However, affect spin was not related to well-being outcomes at the within-person level and decreases in affect spin over time were also not associated with levels of emotional exhaustion and job satisfaction.