Urban green spaces (UGS) support physical activity and population health, yet their use depends on more than availability. In rapidly urbanizing cities, such as Casablanca (Morocco), understanding which UGS characteristics residents value is essential to inform equitable planning and health promotion. This study aimed to explore which characteristics of UGS users identify as motivating factors for engaging in physical activity and to analyze how these preferences vary across different sociodemographic groups in Casablanca. A cross-sectional survey was conducted in three UGS in Casablanca. A total of 468 participants completed structured questionnaires codeveloped through a participatory process under the Citizen Laboratory for Urban Health (CSU Lab). The survey assessed sociodemographic characteristics, physical activity behaviors, patterns of UGS use, and features valued for engaging in physical activity. Descriptive statistics, bivariate analyses, and multivariable logistic regression models were used. Proximity to home (69%), low pollution (43%), and safety (41%) were the top motivators. Functional aspects, such as facilities (36%), and environmental features, such as vegetation (33%), were also frequently cited. Preferences varied across population groups and contexts. After adjustment, proximity to home was more strongly valued by women, retired participants, and residents of specific districts, while younger adults were more likely to value facilities. Valuing safety was shaped primarily by place of residence, whereas valuing low pollution was less common among unemployed participants. This study demonstrates that urban planning and health promotion strategies must incorporate local user perspectives to effectively and equitably promote physical activity through UGS.