Background and Objectives: Rio Grande do Sul (RS) is one of the Brazilian states with the highest percentage of older adults. However, despite the high rates of HIV/AIDS that have been detected in the general population, there are few scientific investigations regarding its prevalence in the older adult population. Our goal is to identify the annual incidence of AIDS in the population aged 60 or over living in the State of RS, Brazil, from 1997 to 2017, and to compare the sex differences in infection rates. Methods: This was a time-series ecological study. Information on annual AIDS notifications was collected on TABNET, and population data of RS was collected on TABNET and the website of the Foundation of Economy and Statistics (FEE) of RS. The annual incidence was calculated per 100,000 inhabitants. Results: Between 1997 and 2017, 3,697 AIDS cases in older adults were notified in RS. In the comparison between 1997 and 2017, the annual incidence of AIDS in older adults in RS increased from 3.92 to 13.71/100,000 inhabitants, and a 249.93% increase (340.49% among men and 171.50% among women). Conclusion: The percentage of AIDS diagnostic in RS was six times higher in older adults than in the general population. The rate for men was almost twice as high as that for women. This may be due to increased life expectancy and other factors related to sexual behavior, such as medications for erectile dysfunction and hormonal replacement, and communication technologies.