Sport leagues have been critiqued for their cartel-like behavior, monopsony power, and many occupational health risks to athletes. Athlete-owned sports leagues are an alternative way of organizing professional sport that may benefit athletes and the industry. This article examines the viability of athlete-owned leagues by reviewing theory and research on worker-owned firms and applying the findings to sports leagues with athlete ownership, with a focus on the Premier Lacrosse League. Five criteria are shown to affect the viability of worker ownership: heterogeneity of interests, capital-labor ratios, time horizons, motivation and efficiency, and conflict with capitalists. When applied to the sport industry, athlete ownership is likely in sports like beach volleyball and skateboarding but unlikely in sports like American football and soccer. Athlete-owned sports leagues have some benefits when compared with capitalist-owned leagues, but they will struggle in markets with incumbents.