This study examined the explanatory models of bulimia nervosa (BN) held by members of professionals in the medical, psychological, and allied health fields; the general public; and female university students. The participants (N = 787) were presented with 44 potential causal explanations for BN and were asked to rate the importance of each in the development of this condition on a 5-point rating scale (“unimportant” to “extremely important”). Principal component analysis identified four causal components. These were interpreted as corresponding to (1) socio-cultural pressure, (2) eating and dieting practices, (3) family dynamics, and (4) psychological vulnerability. A high degree of consistency in the mean ratings for the four causal components was observed among the professional groups. However, important differences were found between the professional and the lay respondents in their beliefs about the role of socio-cultural pressure, eating and dieting practices, and family dynamics in the development of BN. The congruence in beliefs among the professionals groups would contribute to the ease of interdisciplinary collaboration required in the multi-modal treatment approach to BN. However, the differences observed between the professional and lay groups may have implications for educational and preventative strategies for BN.