PurposeThis study aimed to explore the determinants of household food waste behavior to mitigate the negative effects of consumption on climate change through a model that extends the theory of planned behavior (TPB) by integrating motivations to reduce food waste – in addition to moral norms – as well as situational factors – in addition to planning and shopping routines – that affect food waste.Design/methodology/approachOnline self-report questionnaires were used to collect empirical data in Taiwan; a total of 304 responses were retrieved. Two-step structural equation modeling was subsequently conducted.FindingsThe results indicated that the extended TPB model, which notably included motivations to reduce food waste and moral norms regarding reducing food waste, explained 56.84% of the variance in intention not to waste food. Perceived behavioral control regarding reducing food waste was associated with food planning and shopping routines. Intention not to waste food, food shopping routines, and situational factors were determinants of food waste behavior and explained 15.72% of the variance in food waste behavior.Originality/valueThe main theoretical contribution of this study is that the extended TPB model that includes both moral norms and motivation to reduce food waste elucidates the role of motivations in the formation of attitudes. In addition, not only intention not to waste food and shopping routines but also situational factors explained food waste behavior. These findings provide practical and policy implications for enhancing people's intention not to waste food and for reducing their actual food waste behavior.