Paternal smoking is highly prevalent in Asia, and tobacco may account for a large proportion of household expenditures among poor families. We sought to characterise the relationship between paternal smoking, child malnutrition and food expenditures.

Data on smoking, household expenditures and child malnutrition were examined in a stratified multistage cluster sample of households in the Indonesia nutrition surveillance system. Main outcome measures were child wasting (weight-for-height Z-score < − 2), underweight (weight-for-age Z-score < − 2) and stunting (height-for-age Z-score < − 2), and severe wasting, underweight and stunting (defined by respective Z-scores < − 3).

In total, 175 583 households from urban slum areas in Indonesia.

Children 0–59 months of age.

The prevalence of paternal smoking was 73.8%. After adjusting for child gender and age, maternal age and education, and weekly per capita household expenditures, paternal smoking was associated with child stunting (odds ratio (OR) = 1.11, 95% confidence interval (CI) 1.08–1.14, P < 0.0001), severe wasting (OR = 1.17, 95% CI 1.03–1.33, P = 0.018) and severe stunting (OR = 1.09, 95% CI 1.04–1.15, P < 0.001). In households where the father was a smoker, tobacco accounted for 22% of weekly per capita household expenditures, with less money spent on food compared with households in which the father was a non-smoker.

Among poor families in urban slum areas of Indonesia, paternal smoking diverts household money from food to tobacco and exacerbates child malnutrition.