The present study described the development of the Mentor Behaviour Rating Scale. In the Dutch secondary educational system, the mentor is a teacher responsible for individual students' academic and socio-emotional progress throughout the academic year. In order to assess the mentor behaviours conducive to pupils' acceptance levels of their particular mentor, two studies were conducted. In the first study, students (n = 625) rated their mentor on 44 items. Through factor analysis this was reduced to 18 items. In the second study, the reduced scale was administered to 745 students. This revealed the existence of two factors, Respect and Humour. These two mentor behavioural factors were highly predictive of the acceptance levels of students (R2 = 0.52).