According to the United States Census Bureau, the CDP has a total area of . Plainview is on the Nassau County side of the border with Suffolk County. On the Nassau side it borders the hamlets of Bethpage, Hicksville, Old Bethpage, Syosset, and Woodbury. On the Suffolk side, its primary border is with Melville, but also touches West Hills.
according to the united states census bureau the cdp has a total area of  plainview is on the nassau county side of the border with suffolk county on the nassau side it borders the hamlets of bethpage hicksville old bethpage syosset and woodbury on the suffolk side its primary border is with melville but also touches west hills