Teaching is considered a profession in which emotions have a prominent role and it is commonly mentioned in the literature that emotions should be taken into consideration in research related to teacher identity. However, there are limited studies in the accessible literature that investigate beginning teachers' teacher identity development from an emotional perspective. In this study, the emotional experiences of beginning middle school mathematics teachers in their teacher identity development process were investigated through teacher-written diaries. Seven teachers, who graduated from the same teacher education programme, participated in this study, and wrote diaries about their teaching experiences that have emotional effects on them. Qualitative analysis revealed that beginning teachers' emotional experiences varied: mostly negative (2 participants), balanced (3 participants), and mostly positive (2 participants). Furthermore, exploring participants' emotions provided valuable insights about teacher identity development. Findings were discussed based on the emotion-teacher identity relationship, and implications for teacher education programmes and policymakers were addressed.