Garrett is a city in Keyser Township, DeKalb County, Indiana, United States. The population was 6,286 at the 2010 census. Garrett was platted in 1875 when the Baltimore and Ohio Railroad was extended to that point. It was named for John W. Garrett, president of the Baltimore and Ohio Railroad from 1858 to 1884. Garrett was incorporated as a city in 1875.