Auburndale is a city in Polk County, Florida, United States. The population was 13,507 at the 2010 census. According to the U.S Census estimates of 2019, the city had a population of 16,650. It is p…Auburndale is a city in Polk County, Florida, United States. The population was 13,507 at the 2010 census. According to the U.S Census estimates of 2019, the city had a population of 16,650. It is part of the Lakeland–Winter Haven Metropolitan Statistical Area.