This study evaluated the association between air pollution and hospital admissions due to respiratory and cardiovascular diseases in Cubatão, São Paulo State, Brazil. Generalized additive Poisson regression models were used to model daily concentrations of particulate matter (PM10), sulfur dioxide (SO2), and ozone (O3) and daily hospital admissions counts. Explanatory variables were temperature, relative humidity, day of the week, and holidays. For each increment of 10µg/m³ in PM10, we found an excess of 4.25 % (95%CI: 2.82; 71), 5.74% (95%CI: 3.80; 7.71), and 2.29% (95%CI: 0.86; 3.73) in admissions due to respiratory diseases for all ages, respiratory diseases in children under 5 years old, and cardiovascular diseases in adults over 39 years of age, respectively. For SO2, the increase was 3.51% (IC95%: 1.24; 5.83) for cardiovascular diseases in adults more than 39 years. For O3, the increase was 2.85% (IC95%: 0.77; 4.98) for cardiovascular diseases in adults more than 39 years of age and 3.91% (IC95%: 1.37; 6.51) for respiratory diseases in children under 5 years old. Air pollution has serious impacts on health in Cubatão, thus emphasizing the need for air quality control policies.