Abstract Background Women combining paid job and motherhood may experience a poorer health status than those childless. This risk is expectedly higher among lone mothers due to their greater emotional, social, and economic vulnerability. This study aims to assess the impact of employment characteristics on the health of working mothers and to understand differences between lone and coupled mothers. Methods We used data from the 5th Portuguese National Health Survey from employed women (N = 1,649) aged 25-55 living with a child (<16). We modelled depression (assessed by the Personal Health Questionnaire-8) and less-than-good self-reported health as a function of employment variables (part-time job; self-employment; instable job situation; skill level and sector of activity) using logistic regressions, adjusting for age, family variables, socioeconomic status, and social support. Interaction terms assessed differences between lone and coupled mothers. Results Women in part-time (OR = 3.04, 95%CI=2.97-3.11), high-skilled jobs (OR = 3.57, 95%CI=1.30-1.38), and self-employed (OR = 1.34, 95%CI=1.30-1.38) had higher odds for depression, compared to those working in low-skilled, full time and not self-employed jobs. Less-than-good health was also more likely among those working part-time (OR = 1.34, 95%CI=1.31-1.36) and self-employed (OR = 1.34, 95%CI=1.31-1.37). Mothers' mental health disadvantage was amplified when alone regarding self-employment and part-time jobs. Conclusions Employed mothers' physical and mental health may be harmed by part-time jobs, self-employment, and working in more differentiated jobs. Employed lone mothers may experience greater risks than coupled mothers. Key messages Part-time, high-differentiated jobs or self-employment may harm the physical and mental health of working mothers. Lone mothers are disproportionately impacted by these employment characteristics.