Kankakee is a city located in Kankakee County, Illinois. Kankakee has a 2026 population of 23,535. It is also the county seat of Kankakee County. Kankakee is currently declining at a rate of -0.15% annually and its population has decreased by -1.97% since the most recent census, which recorded a population of 24,007 in 2020.