This case study investigates the complex motivations driving English language learning among students in Indonesian pesantren (Islamic boarding schools), focusing on the interplay of integrative, instrumental, and spiritual factors. We employ a qualitative approach, combining semi-structured interviews, classroom observations, and activity reports to capture the evolving motivations of students from diverse backgrounds. The findings reveal a dynamic blend of motivations, where initial instrumental goals (e.g., career advancement or overseas study) often transition into integrative interests, fueled by global media exposure and cultural curiosity. Moreover, the study identifies spiritual motivation as a unique driver, with students framing English proficiency as a religious duty (ibadah) to disseminate Islamic teachings globally, a dimension absent in secular contexts. Institutional policies, such as mandatory English-speaking days and extracurricular programs, further amplify motivation by creating immersive learning environments. Students also engage in self-directed activities, such as translating song lyrics or reading novels, which inadvertently enhance their language skills. The research contributes to the understanding of language acquisition in religious educational settings, highlighting how cultural, spiritual, and institutional factors collectively shape learning behaviors. By uncovering the distinct role of spiritual motivation, this study offers novel insights into the sociocultural dynamics of language learning, with implications for curriculum design and policy in similar contexts.