The purpose of the current study was to examine Japanese graduate students' professional socialisation experiences while instructing students with disabilities during adapted physical education (APE) practicum experiences. This study, situated in occupational socialisation theory, used a case study design. Seven graduate students (four males and three females), who engaged in weekly APE practicum experiences at a Japanese public university campus, were included in this study. Data sources included individual semi-structured face-to-face interviews. The data were analysed using a constant comparative method, and three themes emerged: (1) "equity and equality of professional caring behaviours"; (2) "collaborative lessons"; and (3) "lack of teaching students with severe and profound disabilities in APE practicum." Based on the graduate students' socialisation experiences during their practicum experiences, we suggest APE graduate programmes develop a series of trainee experiences with public school partnerships to enhance teaching competences, and collaborate with in-service APE and/or special education teachers.