Quality of supervisory practices varies. According to the integrative model of behaviour prediction, supervisors' beliefs may influence practice. This study aimed to examine the belief profiles of general practice supervisors, and their potential relationship with supervisory practice. A cross-sectional study was conducted using Q-methodology to explore supervisors' beliefs and the Maastricht Clinical Teaching Questionnaire to measure self-reported supervisory practice. One-hundred and thirty-nine supervisors took part (76%). The most common belief profile (36.7%) comprised a proactive view of supervisors' roles, strong self-efficacy beliefs and awareness of university norms. It revealed merged identities as clinicians and teachers. The second profile (18.0%) included a belief that supervision essentially involved sharing one's experience, uncertainty about the impact of supervision and about university norms. This profile was consistent with a pre-eminence of supervisors' identities as clinicians. Supervisors with merged identities were more likely to have more experience as supervisors and to engage in other teaching activities. Differences in self-reported supervisory practice were observed but did not reach statistical significance (P = 0.053). Supervisors' beliefs reveal differences in the way they manage their multiple professional identities. Further research should be conducted into whether these differences are developmental and if so how development occurs.