AbstrakPenelitian ini bertujuan untuk memahami perilaku sosial siswa tunagrahita serta pengaruh lingkungan keluarga terhadap perkembangan sosialnya di SLB Negeri 5 Bengkulu. Anak tunagrahita secara umum memiliki keterbatasan kognitif yang berdampak pada kemampuan bersosialisasi, regulasi emosi, dan pengambilan keputusan, sehingga memerlukan dukungan intensif dari sekolah dan keluarga. Studi ini menggunakan metode kualitatif deskriptif dengan pendekatan studi kasus pada seorang siswa tunagrahita berusia 13 tahun. Data diperoleh melalui observasi, wawancara mendalam, dan dokumentasi sekolah, kemudian dianalisis menggunakan teknik grounded theory yang meliputi open coding, axial coding, dan selective coding. Hasil penelitian menunjukkan bahwa perilaku sosial siswa dipengaruhi secara signifikan oleh pola asuh, kualitas interaksi keluarga, dukungan emosional orang tua, serta kondisi psikologis orang tua, seperti stres dan depresi. Ketidakkonsistenan dalam pengasuhan dan minimnya pengawasan keluarga berkontribusi pada munculnya perilaku maladaptif seperti merokok dan membolos, meskipun siswa tetap menunjukkan potensi positif seperti kesopanan dan aspirasi akademik. Studi ini menegaskan bahwa kolaborasi antara keluarga dan sekolah, termasuk bimbingan konseling Islam, memiliki peran penting dalam membentuk perilaku sosial positif pada anak tunagrahita. Pendampingan keluarga, edukasi pola asuh, dan penguatan dukungan sosial menjadi strategi yang direkomendasikan untuk meningkatkan kemampuan sosial anak secara lebih optimal. AbstractThis study aims to understand the social behavior of students with intellectual disabilities and the influence of the family environment on their social development at SLB Negeri 5 Bengkulu. Students with intellectual disabilities generally have cognitive limitations that affect their ability to socialize, regulate emotions, and make social decisions, thus requiring intensive support from both school and family. This study employed a descriptive qualitative method with a case study approach involving a 13-year-old student with intellectual disabilities. Data were collected through observations, in-depth interviews, and school documentation, then analyzed using grounded theory techniques, including open coding, axial coding, and selective coding. The findings indicate that the student’s social behavior is significantly influenced by parenting patterns, the quality of family interactions, parental emotional support, as well as the psychological condition of parents, such as stress and depression. Inconsistent parenting and limited supervision contribute to the emergence of maladaptive behaviors such as smoking and skipping classes, although the student still shows positive potential, including politeness and academic aspirations. This study highlights that collaboration between family and school, including Islamic counseling guidance, plays an essential role in fostering positive social behavior in students with intellectual disabilities. Family empowerment, parenting education, and strengthening social support are recommended strategies to enhance children’s social abilities more optimally.