Household food waste poses significant challenges to food security and environmental sustainability, yet evidence from low- and middle-income developing countries remains limited. This study investigates the determinants of household staple-food wastage in urban Bahawalpur, Pakistan, using chapatti disposal as the outcome. Extending the Theory of Planned Behavior, it incorporates a composite Maqasid al-Shariah Index to capture religious and ethical orientation, alongside household structure, residential location, education, food-purchasing responsibility, women’s expenditure monitoring, and per-capita food expenditure. Primary survey data were collected from 433 households, with 424 included in the analytical sample. Binary logistic regression served as the principal model, supported by a robustness specification treating expenditure monitoring as a four-level categorical variable and a negative binomial model examining the daily quantity of discarded chapatti. The results show that 59.7% of households reported chapatti wastage. Joint households had approximately half the odds of waste compared with nuclear households, while frequent expenditure monitoring by women was associated with 55.6% lower odds than no monitoring. Conversely, shared food-purchasing responsibility increased the odds of wastage by 61.3% relative to sole female responsibility. Unexpectedly, stronger Maqasid al-Shariah alignment was associated with higher odds of disposal, although the index was insignificant in the quantity model. Household structure, residential location, and the number of adults predicted discarded quantities. Overall, three hypotheses were supported, one partially supported, and four rejected, indicating a weaker attitudinal pathway. Policy recommendations include religiously grounded awareness campaigns, expenditure-tracking in financial-literacy programmes, joint meal-planning tools, and targeted municipal interventions for middle-income nuclear households. The study’s limitations include self-reported, cross-sectional data, a single staple-food focus, and modest explanatory power; therefore, the findings establish associations rather than causal relationships.