The COVID-19 pandemic has led to the closure of many fitness centers and has significantly affected the behavioral intentions of gym-goers. This study aimed to determine factors affecting the behavioral intentions of gym-goers regarding fitness centers during the COVID-19 pandemic in the Philippines by utilizing the Physical Activity Maintenance Theory within the framework of Social Cognitive Theory. A total of 1048 gym-goers voluntarily answered an online, self-administered survey comprising 68 questions. Structural Equation Modeling indicated that physical activity maintenance through understanding COVID-19 and self-motivation had the highest significant effect on behavioral intentions. Interestingly, life stress was found to have a significant negative direct effect on physical activity maintenance. The current study is one of the first to have analyzed factors affecting the behavioral intentions of gym-goers during the COVID-19 pandemic. Finally, the application of Physical Activity Maintenance Theory and Social Cognitive Theory in this study provided accurate predictors of behavioral intention. As a result, this integrated model could serve as a theoretical foundation that could be applied and extended to assess behavioral intentions among gym-goers during the COVID-19 pandemic worldwide.