<![CDATA[Social-emotional development in early childhood is formed through repeated social experiences in which children recognize feelings, negotiate roles, follow shared rules, and learn to respond to others. This study aims to describe how cooperative play facilitates children's social-emotional development at KB Puspa Melati, Jember. A descriptive qualitative approach was employed. The research was conducted from February August 2026, with intensive fieldwork in May-June 2026. Five adult informants were selected purposively, comprising the head of the learning center, two teachers, and two parents. Data were collected through overt observation, semi-structured interviews, and documentation, and analyzed interactively through data condensation/reduction, data display, and conclusion drawing. Trustworthiness was strengthened through prolonged engagement, persistent observation, source triangulation, and technique triangulation. The findings show that cooperative play operates effectively when embedded in a broader pedagogical ecology habituation, teacher scaffolding, and school-home continuity. Children's self-awareness was supported by emotionally safe routines and opportunities for expression; responsibility developed through shared rules, turn-taking, tidying up materials, and apologizing after conflict; and prosocial behavior appeared through helping, sharing, cooperation, and empathy. Role-play and group construction activities also created authentic situations for communication, collective decision-making, and emotion regulation. Challenges such as competition for roles, uneven participation, and conflict did not merely constitute obstacles; with teacher facilitation, they became learning moments for negotiation and self-regulation. The study concludes that cooperative play should be understood not as a stand-alone technique but as a relational learning space whose social-emotional value depends on consistent facilitation and continuity of habituation across school and family contexts.]]>
