Objectives: The aim of this study was to examine whether the association between employment contract and self-rated health differs by household structure in a representative sample of employees in Japan. Methods: The participants were 81,441 male and 64,471 female employees aged 18–59 years who had participated in the 2010 Comprehensive Survey of Living Conditions. We assessed the interactive effect of employment contract (permanent or precarious) and household structure (couple only, couple with children, single parent, single person, or other multi-person) on fair/poor health, adjusting for covariates by using logistic regression. We then calculated the relative poverty rate by employment contract and household structure. Results: The interaction effect was significant for women ( p <0.001) but not for men ( p =0.413). A higher percentage of female precarious workers who lived in single-parent households (20.2%) reported fair/poor health compared with those in other types of households (10.4–13.2%), although the prevalence of fair/poor health did not differ substantially by household structure among female permanent workers. The relative poverty rates of female precarious workers who lived in single-parent households were higher compared with those of other female workers. Conclusions: Our results suggest that female precarious workers are not a homogeneous group and that those living in single-parent households suffer from poor health due to low income and insufficient coverage by insurance firms and family-based safety nets.(J Occup Health 2014; 56: 339-346)