Teacher transition between year levels is common practice in many primary schools in New Zealand; however, it is not always perceived as an opportunity for teachers' continuing professional development (CPD). This article reports on a case study that explored four primary school teachers' experiences of transition between year levels. The teachers all experienced CPD and identified that transition between year levels improved their teaching practice and knowledge of The New Zealand Curriculum. In general, the teachers felt they benefitted from their transition in terms of gaining a broader understanding of their schools, respect from their peers and career advancement. Two important factors that emerged from the study as having a significant influence on teacher transition were: the role of mentors, and school culture and leadership. The article concludes that because transition between year levels seems to provide a variety of opportunities for teachers' positive CPD, this practice could be more widely acknowledged and promoted.