Fort Walton Beach is a city in southern Okaloosa County, Florida, United States. As of 2010, the population estimate for Fort Walton Beach was 19,507 recorded by the U.S. Census Bureau. It is the principal city of the Fort Walton Beach?Crestview?Destin Metropolitan Statistical Area.Fort Walton Beach is a year-round fishing and beach resort community. Its busiest time of the year is the summer, causing a boost to the local economy because of seasonal human migration.