Caro is a city in and the county seat of Tuscola County, Michigan, United States. The population was 4,328 at the 2020 census and 4,145 at th…Caro is a city in and the county seat of Tuscola County, Michigan, United States. The population was 4,328 at the 2020 census and 4,145 at the 2000 census. Caro is located northeast of Flint and east of Saginaw in Michigan's Upper Thumb region.