The performance of elite athletes is at the forefront of attention in sports science, with a predominant focus on technical, physiological, mental, or contextual factors that can be leveraged to optimize athlete performance. Athletes’ off-sports activities, however, remain largely unexplored. What is it that elite athletes do in their off-sports time, and how are their off-sports activities related to sports experiences and outcomes? With this qualitative study, we aim to illuminate athletes’ off-sports activities and their implications for sports outcomes. We collected listings of off-sports activities from 46 professional soccer players and interviewed 15 elite speed skaters about their off-sports activities and their potential to enrich or interfere with their sports domain. The resulting category framework of off-sports activities comprises eight categories, reflecting social, cognitive, and physical off-sports activities. Next, the speed skaters described beneficial spillover experiences for active, high-effort mastery-oriented off-sports activities. However, such activities could also cause fatigue if not balanced with sufficient, more passive, restful activities. In all, athletes did experience spillover from non-sports to sports and their qualitative accounts reveal several antecedents, mechanisms, and outcomes of spillover, supporting the process view of the work–home resources (W-HR) model (Ten Brummelhuis & Bakker, 2012).