Background: The utility of the theory of planned behaviour (TPB) in predicting the intentions of care staff to encourage healthy eating behaviour in those they supported was examined. Method: A quantitative, within-participant, questionnaire based design was used with 112 carers to assess the performance of two TPB models. The first contained the variables: attitude, subjective norm and perceived behavioural control. The second had additional variables of self efficacy and self identity. Results: Model 1 accounted for 31% of the variance with all three variables being significant predictors. Adding variables increased the overall predictive power of the model by 4%, but resulted in a reduction in the predictive power of the individual variables. Conclusion: The results suggests the TPB is a useful model for predicting carer intentions in relation to the diet of those they support, with their perceptions of the attitudes of others towards healthy eating being a key influential factor. Ways in which this may inform interventions to improve the overall health of people with intellectual disabilities are discussed.