Dowling College originated in 1955 when Adelphi College offered extension classes in Port Jefferson, Riverhead, and Sayville. In 1959, at the urging of community leaders, Adelphi Suffolk College became the first four year, degree granting liberal arts institution in Suffolk County, housed in an old public school building in Sayville. In January 1963, Adelphi Suffolk College purchased the former W.K. Vanderbilt estate in Oakdale and began developing as an important educational force on Long Island.

In 1968, the College severed its ties with Adelphi and was renamed after its chief benefactor, Robert Dowling, a noted city planner, philanthropist, and aviator.