Objective To analyze the influence of nursing workload on the occurrence of healthcare associated infection (HAI) in patients in the intensive care unit (ICU), according to type of treatment. Method Retrospective cohort study developed in nine ICUs in São Paulo, Brazil, from September to December 2012. Nursing workload was measured by the Nursing Activities Score (NAS). The Student's t and Fisher's exact tests and logistic regressions were used in the analyses. Results The sample was composed of 835 patients (54.3±17.3 years; 57.5% male), of which 12.5% acquired HAI in the ICU. The NAS of the patients admitted for clinical treatment was 71.3±10.9, and for surgery 71.6±9.2. Length of stay in ICU and severity were predictive factors for occurrence of HAI in patients admitted to the unit for clinical or surgical treatment, and male sex only for surgical patients. When considering the admissions independent of type of treatment, in addition to the variables mentioned above, index of comorbidities also remained in the regression model. The NAS was not a predictive factor of HAI. Conclusion Nursing workload did not influence occurrence of HAI in the patients included in this study.