Objectives: This study explores how urban young adults practice active living and use community assets. Methods: A qualitative case study was conducted in Seoul on young adults (aged 19–39 years) in areas with low physical activity rates. A total of 30 in-depth interviews were conducted. Data were analyzed using a pattern-finding approach to explore the meaning of active living, challenges in its practice, the role of community assets in supporting active living, and its relationship with urban young adults’ health. Results: Four key themes emerged: (1) Young adults perceived active living as a multifaceted practice that supports physical health, emotional stability, and social connection. (2) They actively used diverse community assets, including local parks, public programs, digital platforms, and peer networks, tailoring them to their daily routines. (3) A gap was noted between available community assets and young adults’ daily routines, particularly in areas with systemic constraints such as limited infrastructure, inflexible schedules, and spatial fragmentation. (4) Active living was practiced as a contextually adjusted and flexible routine shaped by everyday conditions like time availability, financial constraints, and access rather than pursued as an aspirational lifestyle. Conclusion: Findings suggest that active living should be integrated into daily urban life through flexible, context-sensitive strategies. By leveraging both physical and digital community assets, future interventions must reduce structural barriers and support accessible, sustainable practices aligned with young adults’ living realities.