Objective: The aim of this study was to establish associations between personality and BMI and assess to what extent these associations translated into predictive relationships. These relationships were then to be scrutinised to investigate whether they existed via direct or indirect mechanisms. Methods: 141 participants were issued an 80 twin-paired adjective personality questionnaire devised by Costa and McCrae coupled with a questionnaire exploring health behaviours. Correlation coefficients were drawn between personality and BMI and with the four associated health behaviours measured in the questionnaire; calorific intake, leisure activity, occupational activity and weight happiness. General linear models (GLM) were then made to map the relationships between these variables and BMI in order to isolate potential pathways connecting BMI to personality. Results: Extraversion, agreeableness and conscientiousness all correlated positively with occupational activity. Neuroticism was correlated negatively with weight happiness as was agreeableness and conscientiousness with respect to BMI. GLMs showed that both extraversion and conscientiousness had a direct effect on BMI with the latter contributing to as much as a 1.0 point change in BMI per standard deviation. Indirect relationships were exhibited between neuroticism and BMI through calorific intake and weight happiness. Conclusions: Initial personality associations proved to translate into relationships via both direct mechanisms and via health behaviours acting as mediators with BMI.