Abstract: Driven by the deepening National Fitness Strategy and rising sports consumption, mass participation sports events have emerged as a key platform for energizing regional development and facilitating integration across cultural, athletic, commercial, and tourism sectors. Focusing on the “social mobilization—resource orchestration—value co-creation” logical chain, this study adopts an exploratory single-case method, taking the Zhejiang Basketball Association City League (ZheBA) as a typical case to systematically analyze the internal mechanism of value co-creation in mass participation sports events. It reveals that the organization and growth of mass participation sports events rely on a combination of top-down administrative mobilization and bottom-up organizational efforts. Through the selection of grassroots participants, expansion of consumption scenarios, and integration of digital technologies, these events effectively orchestrate resources to co-create value across cultural, emotional, social, and economic dimensions. Nonetheless, events like ZheBA continue to face challenges pertaining to horizontal coordination and vertical depth in social mobilization, strategic resource allocation, and the comprehensive realization of co-created value. To address these, the study proposes implementing dual mobilization strategies that blend administrative and organizational approaches, focusing on both consumption and experiential needs, and establishing mechanisms for sustainable value conversion and feedback. These measures are posited to promote the integrated development of mass participation and competitive sports, thereby contributing to the accelerated realization of a sports powerhouse.