Drawing on conservation of resources theory (Hobfoll, 1989) and the model of proactive motivation (Parker, Bindl, & Strauss, 2010), this research employs experience sampling methods to examine how employees' off-job experiences during the evening relate to their proactive behavior at work the next day. A multilevel path analysis of data from 183 employees across 10 workdays indicated that various types of off-job experiences in the evening had differential effects on daily proactive behavior during the subsequent workday, and the psychological mechanisms underlying these varied relationships were distinct. Specifically, off-job mastery in the evening related positively to next-morning high-activated positive affect and role breadth self-efficacy, off-job agency in the evening related positively to next-morning role breadth self-efficacy and desire for control, and off-job hassles in the evening related negatively to next-morning high-activated positive affect; next-morning high-activated positive affect, role breadth self-efficacy, and desire for control, in turn, predicted next-day proactive behavior. Off-job relaxation in the evening related positively to next-morning low-activated positive affect, and off-job detachment in the evening had a decreasingly positive curvilinear relationship with next-morning low-activated positive affect. However, as expected, these two types of off-job experiences and low-activated positive affect did not relate to next-day proactive behavior. (PsycINFO Database Record (c) 2019 APA, all rights reserved).