Peru has one of the highest informal employment rates in Latin America (73%). Previous studies have shown higher prevalence of poor self-perceived health (P-SPH) in informal workers compared to formal. The study’s aim is to analyse the role of working conditions in the association between informality and SPH in urban working population in Peru. We conducted a cross-sectional study based on 3098 workers from the working conditions survey of Peru 2017. Prevalence of P-SPH and exposure to poor working conditions were calculated separated by formal and informal employment and stratified by sex. Poisson regression models were used to assess the association between P-SPH and informal employment, with its prevalence ratios (PR) crude and adjusted for working conditions. Informal employment was 76% in women and 66% in men. Informal workers were more exposed to poor working conditions than formals and reported worse SPH. Workers in informal employment showed higher risk of P-SPH than formals: PR 1.38 [95% CI: 1.16 – 1.64] in women and PR 1.27 [95% CI: 1.08 – 1.49] in men. Adjustment by working conditions weakened the association in both sexes. In women, this association was only partially explained by worse working conditions 1.23 [95% CI: 1.04 – 1.46]. The negative effect on informal workers’ health is partially explained by poor working conditions. However, there is a part of the effect explained by informality per se.