Johnson, 69, agreed to a one-year pact and will move into a front-office consulting role after next season.
Johnson guided the Nationals to 98 regular season wins this year, the best in the major leagues. Washington won the National League East title, the first pennant of any kind since the franchise moved to the nation's capital from Montreal before the 2005 season.
Johnson's previous contract expired this fall.
Notable deaths of 2014 [PHOTOS]