Down syndrome is a developmental condition characterized by heterogeneous patterns of communication and social participation. The manifestation of social-communicative abilities is not always consistent across all contexts; therefore, understanding students’ behavior requires consideration of the interaction between individual characteristics and the environment. This study aims to explore the social-communicative characteristics of two students with Down syndrome in a special education school by examining communication, social participation, peer interactions, attention, task engagement, and behavioral responses in different contexts. The study employed a qualitative approach using a comparative case study design involving two students ST and SY as well as four informants consisting of parents and classroom teachers. Data were collected through observation, semi-structured interviews, and analysis of educational documents. Data analysis was conducted using thematic analysis, while data credibility was strengthened through triangulation of sources and methods. The results indicate that the social-communicative characteristics of both students are heterogeneous and contextual. ST demonstrated increased participation, verbal expression, and imitation skills in meaningful activities but still exhibited selective peer interactions, difficulty sustaining attention, task refusal, and slow task completion. Meanwhile, SY’s social-communicative characteristics remained relatively stable following the transition to a higher level of education. These findings suggest that assessment and instruction for students with Down syndrome should be tailored to individual profiles, activity characteristics, and environmental conditions that support optimal communication and participation.