This study explored the identity formation of Mario, an English instructor who taught young learners in a tuition center. Using a narrative inquiry approach, the research investigated how Mario's personal and professional experiences shaped his evolving identity as a language instructor in a nonformal educational context. The data were collected through in-depth, semi-structured interviews conducted in English and analyzed thematically based on Wenger’s (1998) theory of identity through engagement, imagination, alignment, and negotiation of meaning. The findings revealed that Mario's identity formation was a continuous process influenced by his early exposure to English, reflective teaching practices, adaptation to the unique challenges of young learners, and ongoing negotiation with his professional role. His teaching journey highlighted the significance of context, especially the structure and culture of tuition centers, in shaping instructional approaches and identity development. This study provided a deeper understanding of how personal experiences and institutional environments intertwined in the construction of an English instructor’s identity. The results offered practical insights for prospective teachers of young learners and contributed to the literature on teacher identity in nonformal settings. It also emphasized the role of narrative inquiry in capturing complex, evolving experiences in teacher development.