This paper reports on how Maria (pseudonym), a non-native English speaker (NNES) and preservice teacher (PST) of English as an additional language (EAL), developed her professional identity during the practicum in an Australian secondary school. Drawing on activity theory, the study identified contradictions in Maria's practicum activity and examined how Maria's professional identity developed through her negotiation of the contradictions. Data included interviews with Maria before, during and after the practicum, her reflections, an interview with her school mentor (Ms Davies, pseudonym), and relevant documents. The findings reveal that Maria experienced contradictions between her multiple identities of NNES, student, becoming teacher, and classroom teacher, between her mentor's teaching approach and that of her own, and between her practice and rules. The findings provide implications for researching teacher identity and supporting preservice EAL teachers in developing productive teacher identities during the practicum.