Introduction Informal employment is an employment condition and an important social determinant of health. Although it can represent a serious problem for public health, it has been seldom studied in Chile as in other countries. The aim of this study was to determine if there is a relationship between informal employment and health among different groups of workers in Chile.

Methods Cross-sectional study with data for 8,357 workers from the first Chilean work, employment health and quality of life survey (2009–2010). We grouped workers as formal or informal according to contractual situation and workplace for dependent workers, educational level for self-employed workers, and number of employees for employers, and then classified these groups into dependent formal, non-dependent formal, dependent informal and non-dependent informal workers. Descriptive analyses stratified by sex and Poisson regression models with prevalence ratios (PR) adjusted by age were used to quantify the association between forms of employment and self-rated health (single item) and mental health (GHQ12). Dependent formal workers were considered the reference group.

Results There was a positive and statistically significant association between informal employment and poor self-rated and mental health in both women and men. The strongest associations with self-rated health were observed among women in informal dependent work (PR = 2.35, 95% CI: 1.71–3.22) and informal non-dependent work (PR = 2.13, 95% CI: 1.65–2.77). Regarding mental health, the association was strongest in men (PR = 2.39, 95% CI: 1.55–3.68) and women (PR = 2.06, 95% CI: 1.26–3.36) in dependent informal jobs.

Conclusions This study found a consistent relationship between informal employment and poor self-reported health and mental health, which appears to be stronger among women than men. Further research is required to further assess and understand the impact of informal employment on workers’ health.