5 | 127 Career, family, and sport participation: a simultaneous exhibition? ABSTRACT Earlier studies show that major life events marking the transition to adulthood affect sport participation. However, empirical insights on the explanatory mechanisms behind these effects are scarce. This study aims to open this “black box” and fill the gap with narrative data in response to the question: Why and how do people change their sport behaviour during the transition to adulthood when major life events occur? From the narratives of 46 Dutch adults, we learn that becoming and being a student, professional, partner and parent confronted the participants with new, more adult roles, responsibilities and activities. As a result, they perceived changes in temporal, social, physical, mental and/or economic resources, and experienced new opportunities and constraints for sport participation. Therefore, participants re-evaluated their priorities and reconsideredwhether or not andhow to integrate practising sport in their new life situations. In general, participating in sport was deprioritised and more challenging after experiencing the major life events. However, there is diversity in the choices that people make regarding (changing) their sport participation during the transition to adulthood, whereby the narratives teach us that the choices largely depended on the participants’ willingness to structurally incorporate sport activities in their new life situations, and on if they saw a way to do so. Based on the insights, we argue that people could be motivated and empowered to sustain sport participation during the transition to adulthood, by providing them with sport concepts that respond to their motivations and reconfiguration of resources, fitting the new life situation as a student, professional, partners or parents. We conclude with some recommendations for practise on how this could be done. Previous drafts of this chapter have been presented in October 2018 at the expert meeting of the POLicy and politics In Sport (POLIS) research-network in Arnhem (The Netherlands), in June 2019 at the European Association for Sociology of Sport (EASS) conference in Bø (Norway), and in August 2019 at the “Dutchies explain” symposium for a delegation of the Swedish Sport Federation in Arnhem (The Netherlands). Co-authors are Associate Lector E. Jansen, S. Cobussen and M. Hofmeijer.