Purpose To elucidate the factors influencing suboptimal food (SF) purchase intention among Taiwanese consumers, this study extended the theory of planned behaviour (TPB) model by incorporating driving factors that encourage purchasing of SFs, that is, incorporating food waste awareness and personal norms. The inhibiting moderator of health consciousness and facilitating moderator of price consciousness were also considered. Design/methodology/approach A total of 305 online questionnaire responses were analysed. Moderated regression analysis was performed to test the hypotheses proposed in this study. Findings Consumer attitudes toward purchasing SFs and perceived behavioural control as well as their food waste awareness and personal norms are determinants of their SF purchase intention. Health consciousness inhibits SF purchase intention, and price consciousness promotes SF purchase intention. In addition, the moderating effect of health consciousness reverses the positive relationship between personal norms and SF purchase intention, turning the relationship negative. However, the moderating effect of price consciousness strengthens the positive relationship between personal norms and SF purchase intention. Originality/value In addition to extending the TPB model, this study considered the main effects and moderating effects of health consciousness and price consciousness on consumers’ intention to purchase SF. The research findings contribute to the understanding of the relevant factors that influence Taiwanese consumers’ SF purchase intention. The study also outlines the implications of its findings in terms of encouraging consumers to purchase SFs to reduce food waste.