It extends for 300.71 miles (483.95 km) from an interchange with NY 17 (Future Interstate 86) in the Southern Tier to the US–Canada border in the state's North Country, where it continues into Quebec as Route 138.

The route follows the East Branch northeast to Downsville, where it meets NY 206.

[4] New York Governor David Paterson designated the stretch of NY 30 within Delaware County the "David C. Brinkerhoff Memorial Highway", after the New York State Trooper who was slain in pursuit of Travis Trimm near the village on April 25, 2007.

[4] North of Grand Gorge, NY 30 crosses into Schoharie County and intersects NY 990V, one of four reference routes in New York signed as a touring route, near the northeastern edge of the Schoharie Reservoir in Gilboa.

The route meets the New York State Thruway (I-90) and NY 5S via separate interchanges before heading downhill as a four-lane divided highway approaching the Mohawk River (here part of the Erie Canal).

Historically, the bridge over the river was a straight line to Market Street, which is visible as one approaches northbound.

[7][8] After the splits rejoin, NY 30 continues on Market Street and leaves the city and, for all purposes, the county.

0.25 miles (0.40 km), NY 30 turns left toward Mayfield; CR 155 continues eastward.

[4] Route 30 made up part of the privately owned Middletown and Roxbury Turnpike.

[10] The highway was about 23 miles (37 km) long, as that is the current stretch of Route 30 from Middletown to Roxbury.

[10] Prior to 1930, the modern routing of NY 30 carried a large number of designations.

From Mayfield north to Malone, most of the current routing of NY 30 carried a designation.

NY 30 was originally routed along the base of Toepath Mountain near Fultonham and along a pair of village streets in Breakabeen.

In the 1950s, a proposal was made to reroute NY 30 onto a new routing in the base of the valley surrounding Schoharie Creek.

[12] The route was realigned c. 1961 to follow a new highway along the western lakeshore, bypassing Northville entirely.

[19] The latter intersection was the site of a deadly limousine crash in October 2018 that killed 20 people.

Along the way, it connects to several major east–west highways, including US 20 in Esperance and the New York State Thruway in Fultonville.