This study aims to analyze the factors that influence the loyalty of Jabodetabek Commuter Line (KRL) passengers, using the Theory of Planned Behavior (TPB) perspective. This study focuses on the influence of attitudes, social norms, perceived behavioral control, and satisfaction on the intention to be loyal to KRL. The method used in this study is quantitative, employing Structural Equation Modeling (SEM) using Smart PLS software to measure the relationships between latent variables and related indicators. The results of the study indicate that the factors influencing KRL user loyalty are social norms, including influences from family, friends, and superiors. Behavioral control also has a significant influence, particularly regarding availability, travel time, and punctuality. Although positive attitudes toward the KRL do not directly influence loyalty, positive user experiences related to service quality, such as comfort and safety, play a significant role in enhancing loyalty. User satisfaction with KRL services was also found to have a positive effect on the intention to be loyal, highlighting the importance of improving service quality in maintaining and enhancing satisfaction. This study suggests improving service quality, enhancing mode integration, and providing incentives to boost passenger loyalty, as well as strengthening social norms that support the use of public transportation. These findings contribute to transportation planning in densely populated urban areas like Jabodetabek to achieve sustainable transportation systems.