Despite the accumulating body of research on teacher cognition and teacher learning in the field of second language (L2) teacher education over the past 2 decades, few studies have followed novice L2 teachers’ development over time, and still fewer have focused specifically on teacher identity development. This study begins to fill this gap by examining how novice English-as-a-second-language (ESL) teachers learn to teach and how this learning-in-practice experience shapes their identities as teachers. For 1 academic year, we followed 2 graduate students in a Master of Arts for Teachers of English to Speakers of Other Languages program at a U.S. university as they taught their own ESL classes for the first time. In analyzing the 2 case studies from a situated learning perspective, we show an intertwined relationship between novice teachers’ identity development and their changing classroom practice. Based on our findings, we argue for the need to include a deeper understanding of teacher identity development in the knowledge base of L2 teacher education.