OBJECTIVES: The objectives were to explore the determinants of intention to adopt Pharmacy Value Added Services (PVAS) using the Theory of Planned Behaviour (TPB). Additionally, we assess the role of knowledge and expectations in mediating the effects of TPB constructs on intentions. METHODS: A two phase mixed methodology involving a qualitative exploration and a quantitative phase was conducted among 5 public health facilities in Negeri Sembilan, Malaysia. A self-administered questionnaire survey was administered to 410 respondents from five different health centres in city of Seremban in the state of Negeri Sembilan, Malaysia. Multiple regression was performed to determine the key determinants of intention to adopt PVAS and mediation analysis to assess the indirect effects of patient’s knowledge and expectations on intentions within the TPB model. The main outcome measures were the effects of subjective norms, perceived behavioural control, attitudes, knowledge and expectations on intentions to adopt PVAS. RESULTS: Subjective norms, perceived behavioural control, knowledge and expectations were significant predictors of intentions to adopt PVAS. Knowledge and expectations were found to exert significant mediating effects on intention. Attitudes, subjective norms, and perceived behavioural control exerted significant effects on patient intention through knowledge and expectations. Ethnicity was also found to be a statistically significant predictor of intentions. CONCLUSIONS: PVAS is still a new pharmacy public health service in Malaysia. We suggest that patient knowledge should be enhanced through appropriate channels and expectations of service quality should be equalized to increase intentions. Further research into specific ethnic predictors are also recommended.