Purpose: The study aims at scrutinizing how the dayah education system develops social capital for students. The objective of this study is also to investigate the ways the social capital in the dayah education system is used for reducing adolescent delinquent behaviours. Hopefully, this study can help inspire other education institutions in efforts to reduce delinquency in adolescence.
 
 Theoretical reference: Social capital in an educational institution can be measured from three indicators including 1) trust and mutual relations, 2) values and norms, and 3) proactive attitudes and social participation (Adam, 2003; Coleman, 1988; Field, 2003; Fukuyama, 2001; Putnam 1993; 2000). Adolescent delinquency is caused by the inability of oneself to reduce their aggressive, violent, and sadistic feelings. It is the output of their lack of emotional maturity and self-concept. Adolescents with low emotional maturity and self-control tend to be reckless and naughty. They fail to develop the essential elements of emotional maturity including self-control, independence, and self-acceptance (see Hurlock, 1996). In the dayah environment, various elements interact with each other involving leaders, teachers, students, curriculum, and facilities.
 
 Method: Using a qualitative research design, this longitudinal case study sought to scrutinize the education system in dayah for developing social capital. This study also investigated how dayah reduces adolescent delinquency via social capital. This longitudinal ethnographic study was conducted for two years from 2021 to 2023.
 
 Results: The findings of this study have shown that dayah educational institution in the development of social capital can be used as a means of: 1) growing social capital through character education, and 2) growing social capital with proactive and participatory attitudes. The followings are the social capital of dayah for reducing adolescent delinquency: 1) trust as social capital for reducing adolescent delinquency, 2) instilling islamic teachings for reducing adolescent delinquency, 3) proactive and participatory attitudes for reducing adolescent social delinquency.
 
 Conclusion: Social capital development in the dayah is done via moral and character education based on Islamic religious values. It is also endorsed by the proactive and participatory attitudes of the students and the surrounding community. In cultivating the students’ moral character, the dayah curriculum teaches character-based knowledge such as tawhid, fiqh, morals, tarbiyah, and Islamic history. In addition, moral and character values based on Islamic teachings are holistically integrated in academic and non-academic activities. Those are instilled in supervision and coaching, adab and ethics teaching, worship and sunnah practices, and self-development that promotes cooperation and mutual help.
 
 Implications of research: As a suggestion for reducing adolescent delinquency and ensuring the development of social capital, educational institutions especially Islamic boarding schools, must be able to revive an academic culture that can grow trust and mutual relations, values and norms, and proactive attitudes.
 
 Originality/value: Researchers examine Dayah's social capital as a built environment seen as a whole from the elements contained in Dayah such as; ash (leader), teachers, students, facilities, infrastructure, curriculum and extra-curriculum learning methods, the role and participation of alumni and parents of students who are the capital to reduce delinquent behavior in teenagers. This is different from previous research which focused on the role of Teungku Dayah as an agent in growing social capital. This research also contributes new ideas in the development of social capital-based Dayah, considering the importance of Dayah in Acehnese society whose role is not only in developing students with good morals but also being directly involved in community activities.