PurposeThis research aims to investigate consumers' food waste prevention behaviour through the lens of an extended theory of planned behaviour. The extension includes the examination of the role of social media usage in affecting consumers' decision-making process of food waste prevention behaviour.Design/methodology/approachA survey questionnaire is developed based on measurement items of previously validated studies. 210 samples are collected and analysed using partial least squares structural equation modelling (PLS-SEM).FindingsThe results show that social media usage has a significant influence on attitude and injunctive norms. In addition, intention can be predicted by injunctive norms, moral norms and perceived behavioural control but not attitude. Lastly, the intention to reduce food waste is a significant predictor of food waste prevention behaviour.Originality/valueOverall, the extended theory of planned behaviour is useful in explaining consumers' food waste prevention behaviour. Interestingly, this study reveals that a negative attitude towards food waste behaviour does not translate into the intention to engage in food waste prevention behaviour. Furthermore, it is found that social media usage plays a significant in shaping consumers' attitudes towards food waste and injunctive norms.