This study aims to explore how English as a Second Language ESL Pre-Service Teachers (PSTs) employ adaptation strategies in response to the surrounding constraining context to develop their professional identities. The research question is "How do pre-service teachers (PSTs) employ adaptation strategies to develop their professional identity (PI) during their simulated teaching class and practicum?". Qualitative data were collected using semi-structured interviews and classroom observation from PSTs in a Malaysian university and public secondary schools in Kuala Lumpur. Findings showed that the positive notions of belonging to a Community of Practice (CoP) proved to be applicable in the simulated teaching class context, so PSTs used their adaptation process of observation-experimentation and evaluation to attempt different teaching practices. Nonetheless, the positive notions of the CoP were inapplicable in the teaching practicum context. Hence, PSTs struggled to construct their Professional Identity (PI) and had to alter their adaptation strategies to negotiate PI construction. The study concludes with some recommendations for further use. Program designers need to consider social interaction and integration within the professional context. That could enable adaptation processes to enhance PSTs' PI development.