This study aims to investigate the interplay between customer attitudes toward sustainable banking practices and their decision-making processes when selecting banks, focusing on the influence of Customer Relationship Management (CRM) systems in this dynamic. The research explores how a major Swedish bank communicates its sustainability efforts through CRM strategies, shaping customer perceptions and engagement. By integrating frameworks of CRM theory, Corporate Social Responsibility (CSR) theory, and the Theory of Planned Behavior (TPB), the study seeks to bridge the gap between theoretical knowledge and practical implementation in sustainable banking. A qualitative research design was employed, utilizing semi-structured interviews with twelve customers of a major Swedish bank. These interviews provided rich, detailed data on customer perceptions, attitudes, and behaviors related to sustainability in banking. Additionally, document analysis of the bank’s annual sustainability report and CRM approaches was conducted to contrast publicized efforts with actual customer perceptions. The major findings reveal that customers prioritize sustainability in their banking decisions and expect banks to adopt and promote sustainable practices. Effective communication of sustainability initiatives through CRM systems significantly enhances customer loyalty and engagement. However, the study also highlights limitations, including the focus on a single bank and geographic region, which may restrict the generalizability of the findings. This research contributes to the theoretical understanding of how sustainability initiatives can be effectively communicated and perceived through CRM systems, enhancing customer engagement and loyalty. It underscores the importance of aligning CRM strategies with sustainability goals, providing practical insights for banks aiming to enhance their sustainability efforts. The findings support the development of more robust theories around the integration of sustainability into CRM and CSR practices, ultimately contributing to global sustainability targets.