Aims: Adherence to prescribed treatment is important for obtaining the desired outcomes in older people care. Polypharmacy is strictly associated with adherence, and complex pharmacotherapy can lead to poor adherence and unexpected outcomes, which are aggravated by older age. The medication regimen complexity index has been proven to be a valid and reliable tool for quantifying the complexity of medication regimens. The objective of the present study was to evaluate the therapeutic complexity of drugs used by older people in a primary care setting in Brazil. Methods: This was a cross-sectional study conducted in 22 basic health units in Brazil. Older people from this sample who were treated in a primary care setting were interviewed after a consultation with a family practice physician. Data were collected from September 2016 to March 2019. Patients aged ≥ 60 years who visited the primary care units were included in the study. Pharmacotherapeutic complexity was assessed according to the medication regimen complexity index. Results: In all, 675 individuals with a mean age of 70 years (±7.1 years) were included. The mean number of drugs prescribed per capita was 2.9 (±1.8). The median medication regimen complexity index for the sample was 8.0, and 26.1% of the patients interviewed had a high medication regimen complexity index. Conclusion: The complexity of the drug regimen was high in almost one-third of the prescriptions analysed. This high complexity might contribute to non-adherence to medication regimens, leading to safety- and effectiveness-related issues. Key words: drug prescriptions, geriatrics, pharmaceutical preparations, polypharmacy, primary health care, older patient.