This chapter uses the Stimulus-Organism-Response (SOR) theory to examine how staff behavior and physical environment quality impact brand loyalty in the fast-food industry, including the roles of brand passion and satisfaction as mediators. Data from 434 customers of a major fast-food chain in the Philippines were analyzed using Partial Least Squares Structural Equation Modeling (PLS-SEM). The study finds that staff behavior affects brand passion, satisfaction, and loyalty, while physical environment quality influences brand passion and satisfaction but not directly brand loyalty. Brand passion and satisfaction are key mediators in these relationships. The study highlights the importance of staff training and an appealing physical environment in building brand loyalty.