Bullying remains a serious issue across various educational institutions, including Islamic boarding schools (pesantren). Although pesantren are widely recognized as educational institutions grounded in Islamic values, bullying may still occur in the form of verbal, physical, psychological, and social abuse. This study aims to analyze the process of internalizing the values of ukhuwah Islamiyah (Islamic brotherhood) as a preventive strategy for reducing bullying behavior among students (santri) at Pondok Pesantren Kitab Kuning Babul Hasanah. This research employed a qualitative approach using a case study design. Data were collected through participant observation, in-depth interviews, documentation, and Focus Group Discussions (FGDs) involving the head of the pesantren, teachers, dormitory supervisors (musyrif), and students. Data were analyzed using the interactive model of Miles, Huberman, and Saldaña, which consists of data condensation, data display, and conclusion drawing and verification. The findings reveal that the internalization of ukhuwah Islamiyah values is implemented through teachers' role modeling, the learning of classical Islamic texts (kitab kuning), congregational worship, deliberative discussions (musyawarah), mutual cooperation (gotong royong), mentoring, and a dormitory supervision system. These strategies successfully foster mutual respect, empathy, solidarity, social responsibility, and collective accountability, thereby reducing the potential for bullying within the pesantren environment. This study proposes the internalization of ukhuwah Islamiyah values as a preventive model that can be adapted and implemented in other Islamic educational institutions.