The route extends along the central parts and North Shore of Long Island for just over 105 miles (169 km) from east midtown Manhattan in New York City to the Cross Sound Ferry terminal at Orient Point on the end of Long Island's North Fork.

At that point, NY 25 turns east onto Jericho Turnpike, which runs along the Queens-Nassau border from Braddock Avenue to 257th Street.

Continuing east through Nassau and western Suffolk counties, NY 25 retains the name Jericho Turnpike.

Two alternate routings exist bearing the designation NY 25 Truck, both along the North Fork.

NY 25 begins near Second Avenue in Manhattan, at the western end of the double-decked Queensboro Bridge spanning the East River and Roosevelt Island.

[4] In Long Island City, NY 25 runs southeast beneath the elevated tracks of the IRT Flushing Line.

At Thompson Avenue, the route turns to run eastward as the multi-lane divided Queens Boulevard, straddling the Flushing Line's elevated structure eastward to 48th Street, at which point the Flushing Line turns northeast onto Roosevelt Avenue and Queens Boulevard becomes 6 lanes in each direction, with main and service roads.

In Elmhurst, the road runs over the eponymous subway line starting at the intersection with Grand Avenue and Broadway.

In Corona, the road intersects the Long Island Expressway (I-495) and the northern terminus of Woodhaven Boulevard.

In Kew Gardens the route is connected to the westbound and eastbound roadways of Union Turnpike and passes over the Jackie Robinson Parkway without access.

[4] In Bellerose, the roadway passes over the Cross Island Parkway and turns east onto Jericho Turnpike.

Four miles (6 km) later, NY 25 encounters the Long Island Expressway one final time at another interchange.

[9] NY 25 continues on the northeastern end of Long Island for the final ten miles (16 km).

At the time, the section of modern NY 25 between the New York City line and Smithtown was state-maintained but unnumbered.

[21][24] From 1920 to 2005, the section of NY 25 that forms the border between New York City and Nassau County was simultaneously named Jamaica Avenue on the westbound (Queens, New York City) side and Jericho Turnpike on the eastbound (Nassau County) side.

[26] The confusion ended where the road wholly entered Nassau County and thus became Jericho Turnpike in both directions.

Legislation renaming the westbound side of NY 25 between Braddock Avenue and the Nassau County line as Jericho Turnpike was signed into law by New York City Mayor Michael Bloomberg on June 6, 2005, and took effect on September 4.

[34] Although some of this section has been dismantled, a portion still exists as modern Forge Road from the Peconic River Bridge to Kroemer Avenue.

The second, a loop providing access to Whalers Road from NY 25, is west of Charles Rose Airport.

It features grade separated ramps, high-speed banked curves, and interstate standard signing.

A traffic light at Manor Road was installed at the time of completion of Splish Splash Water Park in 1991.

There are two separate routes designated NY 25 Truck on the North Fork of Long Island.

Together, they bypass a low railroad bridge that carries the Main Line of the Long Island Rail Road over NY 25 in Laurel and narrow historic streets in Greenport.