State Bike Route 25 begins at the intersection of NY Route 25, NY Route 25A and NY Route 111, a half mile east of the Town of Smithtown central business district and it continues northeast along NY Route 25A and then diverts to local roads in St James, Stony Brook and Setauket, and briefly rejoins NY Route 25A in Setauket. In the scenic Village of Port Jefferson, NY State Bike Route 25 connects with the Port Jefferson-Bridgeport, CT ferry. NY Route 25 State Bike Route 25 continues east from Port Jefferson following local roads for six miles before rejoining NY Route 25A in Sound Beach. Going east from Sound Beach, NY 25 State Bike Route stays on NY Route 25A following a designated bike lane until it merges with NY 25 in Calverton. NY 25 State Bike Route stays on NY Route 25 most of the way out to Orient Point except for a section on local roads in the Town of Riverhead and the Village of Greenport.