Introduction: Alzheimer's disease (AD) is a public health problem in Brazil due to the growing number of older adults in this population. Knowing the prevalence of AD in the Paraná state is essential to improve patients’ quality of life. The objective of the study was to estimate AD prevalence in the state of Paraná, based on the prescription of anticholinesterases, from 2012 to 2017. Methods: Patients diagnosed with AD, aged 60 years or over, who used Brazil’s Unified Public Health System (SUS) and received AD medication from the Department of Pharmaceutical Assistance of the state of Paraná, from 2012 to 2017, were the target population of the present study. The medication data were collected from the Computerized system management and Monitoring of Exceptional Drugs (SISMEDEX), and the population’s data were collected from the Brazilian Institute of Geography and Statistics (IBGE). Results: The sample consisted of 52,687 patients, and the median prevalence of AD in the established period for the state was 642.6/100,000 inhabitants (0.64%). In all ages and macro-regions, women showed the highest prevalence rates. The median prevalence for women in the established period was 755.4/100,000 inhabitants (0.75%). Among men, the median prevalence was 510.2/100,000 inhabitants (0.51%). In the temporal analysis of prevalence, between 2012 and 2017, a reduction of 23% was found in the state rate. The prevalence rate of Paraná for AD is nine times lower than the Brazilian average. Conclusions: Paraná’s prevalence rate for AD is lower than the rates of Brazil and the world, suggesting that AD is underdiagnosed in most municipalities of this state.