Several studies showed that sickness absenteeism has considerable impact on civil service given the increasing number of sick leaves granted to and days off work among employees. Health care workers, especially those in hospitals, represent one of the occupational groups at higher risk of absenteeism. Therefore, establishing the pattern of sickness absenteeism in this group is crucial to implement efficacious preventive measures against work-related diseases. To characterize sickness absenteeism among the nursing and medical staff of a public hospital in São Paulo, Brazil, in the period from 2011 through 2013. Cross-sectional descriptive study conducted in a large hospital in which we analyzed data from January 2011 to December 2013. Employees missed a total of 71,460 days of work along the analyzed period; 3,323 sick leave benefits were granted to 1,533 workers. Nursing assistants and workers in the adult emergency department accounted for the largest number of days off work to a total of 11,460. The most common reasons for sick leaves among emergency department employees were musculoskeletal diseases and mental and behavioral disorders. We detected changes in the morbidity profile of the nursing and medical staff along the analyzed period, characterized by conditions which demand longer time for recovery and return to work.