- Western Terminus:
- Wicks Road (CR 13) in Brentwood
- Eastern Terminus:
- Veterans Highway (NY 454) in Islandia
- 4.80 miles
Suffolk Avenue is an east/west route extending from Brentwood to Islandia. It begins at Wicks Road (CR 13) and runs east, parallel to and just north of the Main Line of the Long Island Rail Road. It is an undivided road, mostly with two lanes, until the traffic light at Carleton Avenue (CR 17) and Wheeler Road (CR 17), where is becomes a divided highway. It continues east to Veterans Highway (NY 454), where it ends.
Suffolk Avenue is one portion of the old alignment of NY 24 from before it was divided into two noncontiguous segments. It is the only such segment that is designated a county route as opposed to a local street.