Studies have demonstrated the negative impact of environmental tobacco smoke (ETS) or parental cigarette smoking on pediatric asthma. Little is known, however, regarding whether there is a gender difference in the effect of household ETS on pediatric asthma. Using a nationwide survey in Taiwan, we examined the relationship between asthma prevalence in the past year and household ETS among children below 12 years of age (N = 3761). We used multivariate regression models to assess odds ratios (ORs) and 95% confidence intervals (CIs) for the association of household ETS and asthma attacks by gender. In about 3% of the sample, parents reported that their children had an asthma attack in the past year, confirmed by physicians. Multivariate logistic regression revealed that household ETS predicted asthma attacks for girls (OR = 3.11, 95%CI = 1.24–7.76) but not for boys. Father’s education was significantly associated with asthma attack for both girls (OR = 1.24, 95%CI = 1.04–1.47) and boys (OR = 1.15, 95%CI = 1.05–1.26). Girls with lower family income were more likely to have had an asthma attack in the last year (OR = .48, 95%CI = .27–.87). The impact of household ETS and family socioeconomic status on asthma attacks differs by gender among children below 12 years.