The highway is split into two segments; the longer western section extends 18.68 miles (30.06 km) from an interchange with Interstate 295 (I-295, named the Clearview Expressway) and NY 25 (Hillside Avenue) in the Queens Village section of the New York City borough of Queens to an intersection with NY 110 in East Farmingdale in the Suffolk County town of Babylon.

NY 24 proceeds southeast along two one-way couplets along Hollis Court Boulevard and 212th Street through dense housing for several blocks (the only unsigned section of the route).

[3] Passing a Long Island Rail Road substation, NY 24 proceeds southeast along the four-lane commercial strip of Hempstead Avenue, intersecting with Springfield Boulevard as it crosses through Queens Village.

A short distance later, the route enters a partial cloverleaf interchange with the Cross Island Parkway's exit 26B.

After crossing the Cross Island Parkway, NY 24 enters Nassau County, changing names to Hempstead Turnpike and passing south of Belmont Park Racetrack and the Belmont Park LIRR station, along with UBS Arena, the home of the New York Islanders of the National Hockey League.

The route crosses through East Elmont before entering Floral Park Crest, where the roadway bends northeast through Hempstead.

The route soon makes a short bend to the southeast, crossing an intersection with New Hyde Park Road and Franklin Avenue later into West Hempstead.

NY 24 then proceeds northeast through downtown Hempstead, remaining a four-lane commercial street through the city, bending south of a local park.

At the junction with Clinton Street, NY 24 bends east for a block, turning northeast again at Peninsula Boulevard.

Just after Earle Ovington Boulevard, the route continues east in to Uniondale and runs alongside the parking lots for Nassau Coliseum, the former home of the Islanders from their 1972 founding until 2015, then 2018 until 2021, when they moved 7.7 miles (12.4 km) west down the pike to UBS Arena.

After the Meadowbrook, NY 24 enters East Meadow, remaining a six-lane boulevard past Merrick Avenue, passing south of Eisenhower Park.

After Carman Avenue, the route passes south of Nassau University Medical Center before returning to the commercial businesses that have surrounded the roadway.

Three blocks to the east, NY 24 condenses to four lanes, entering a partial cloverleaf interchange with the Bethpage State Parkway (exit B3).

A short distance to the east, the route intersects with Secatogue Avenue, which connects to the Farmingdale station to the northwest.

Now in the town of Babylon, retaining the Conklin Street moniker before entering an at-grade junction with NY 110 (Broad Hollow Road) in front of Airport Plaza.

NY 24 proceeds eastward along Edwards Avenue as a four-lane expressway, concurrent with County Route 94 (CR 94) before changing monikers at the corner of South River Road.

At Wood Road Trail, NY 24 bends southeast through Flanders, paralleling the eastern end of Reeves Bay.

A short distance later, the route enters Sears Bellows County Park, soon changing monikers to Riverhead–Hampton Bays Road.

Just after the cloverleaf, NY 24 ends at an intersection with CR 80 (West Montauk Highway) in the community of Hampton Bays.

[13][14] By 1956, the highway had been renamed the Long Island Expressway (LIE) and extended east to Queens Boulevard.