The route, assigned in the mid-1930s, acts as a northern alternate to NY 25, running parallel to its parent for its entire length.

Roughly 0.6 miles (1.0 km) from Winchester Boulevard, NY 25B, facing northeast once more, intersects the west (southbound) frontage road of the Cross Island Parkway in Bellerose.

Upon crossing the parkway, the structures along Hillside Avenue shift from residential to commercial, a trend that remains in place to the Nassau County line.

[6] At the county line, NY 25B breaks from its previous east-northeast alignment and takes a more pronounced northeast routing through New Hyde Park.

A half-mile from the county line, NY 25B enters North New Hyde Park, intersecting Lakeville Road in the center.

[6] Past New Hyde Park Road, the buildings surrounding NY 25B become a balanced mix of commercial and residential structures.

On the eastern edge of the village, NY 25B narrows to two lanes as it crosses the Oyster Bay Branch of the Long Island Rail Road and enters East Williston, where the surroundings shift to residential for the final time.

[6] In the center of the village, NY 25B intersects Roslyn Road before passing by the North Side School two blocks to the east.

Roughly a half-mile from the school, NY 25B enters the village of Old Westbury and passes over the eight-lane Northern State Parkway with no connection between the two.