The sustainable success of sports depends on a well-developed amateur participation base. The important role of amateur participation is transferring to esports, a professionalized form of organized video game competition. While esports has enjoyed considerable popularity, concerns about its viability are growing, as its revenue displays an increasingly slow growth and is small. Recently, amateur esports has been emerging to support esports sustainability, although little is known about mass gamers’ amateur esports participation. To understand the phenomenon and facilitate its development, adopting the serious leisure perspective and affordance theory, we investigate relationships between mass gamers’ video game engagement and their amateur esports participation. Specifically, two serious leisure-based gaming experiences influencing amateur esports participation are identified, enabling us to confirm two game affordances for developing both experiences. This study enriches our knowledge of amateur esports development by explaining how video game engagement facilitates amateur esports participation from a serious leisure perspective.