The highway system of Niagara County, New York, comprises of roads maintained by the New York State Department of Transportation (NYSDOT), the county, and its towns and villages. 31 state-maintained highways enter the county, which account for a combined of the state highway mileage in New York. 21 of the highways are signed state routes; the other 10 are unsigned reference routes. The state roads are supplemented by of county-maintained highways, which carry unsigned county route designations. Niagara County is also served by three byways—the Seaway Trail, the Niagara Historic Trail, and the Niagara Wine Trail.

Highways

Interstate and US Highways

Niagara County is served by three nationally-assigned highways: I-190, an auxiliary Interstate Highway; US 62, a United States Numbered Highway; and US 62's business route through part of Niagara Falls. I-190 heads from Erie County to Niagara County by way of the North Grand Island Bridge over the Niagara River and immediately connects to NY 384, the Niagara Scenic Parkway, and the LaSalle Expressway at a complex interchange on the north side of the bridge in Niagara Falls. The section of I-190 south of NY 384 is also designated as NY 324; however, that route is not signed north of Grand Island. Farther north, I-190 meets US 62 before leaving the city for the town of Lewiston. In Lewiston, the highway trends more to the northwest, crossing NY 31 and NY 104 on its way to the Lewiston-Queenston Bridge over the Niagara River. The bridge carries I-190 to the Canadian border, where it connects to Highway 405 in the province of Ontario.

US 62 enters Niagara County upon crossing Tonawanda Creek northeast of North Tonawanda. It initially heads northwest through the town of Wheatfield as Niagara Falls Boulevard, intersecting NY 425 and NY 429 on its way to a junction with NY 182 near Niagara Falls International Airport. From here, the route takes on a more westerly track as it heads into Niagara Falls. Within the city, US 62 connects to NY 265 and I-190 before splitting into two one-way streets on the east side of downtown. US 62 follows the one-way couplet along Walnut and Ferry avenues (north and southbound, respectively) to its end at NY 104 near the Rainbow Bridge. US 62 Business runs one block to the north of US 62 in downtown Niagara Falls. It follows Pine Avenue from NY 104 just north of downtown to the east end of US 62's one-way couplet.

State touring routes 21 signed state routes—called touring routes by the New York State Department of Transportation—enter Niagara County at some point along their routing.

NY 18

NY 18 begins at NY 104 south of a complex grade-separated interchange that includes NY 18F, NY 104, and the Niagara Scenic Parkway on the eastern edge of the village of Lewiston, north of Niagara Falls. From here NY 18 runs primarily north–south through the western portion of Niagara County to the Lake Ontario shoreline, where it turns eastward to parallel the lake shore across the rest of the county. It crosses into Orleans County at the hamlet of County Line, where NY 18 intersects the north end of NY 269.

NY 18F

NY 18F is an alternate route of NY 18 through northwestern Niagara County. It begins at an interchange with NY 104 and the Niagara Scenic Parkway just east of the village of Lewiston and runs northward alongside the Niagara River to a junction with NY 18 near Four Mile Creek State Park in Porter. NY 18F parallels NY 18 for most of its alignment, taking a more westerly course than its parent. NY 18F is the only remaining suffixed route of NY 18 and was once part of NY 18 itself.

NY 31

NY 31 begins at NY 104 in northern Niagara Falls and travels east–west through central Niagara County as Saunders Settlement Road to the city of Lockport. The route intersects NY 78 on the edge of the Erie Canal in downtown Lockport before continuing east out of the city. Past Lockport, NY 31 passes through the mostly rural eastern portion of the county, serving the village of Middleport before crossing into Orleans County.

NY 31E

NY 31E is an alternate route of NY 31 between the villages of Middleport and Medina. The route heads north from NY 31, overlapping NY 271 through Middleport along Main Street. Just south of the Erie Canal at State Street, NY 31E splits from NY 271, with NY 31E following State Street eastward out of the village. From here, the route loosely parallels NY 31 while following the canal to the Orleans County line.

NY 61

NY 61 is a state highway located almost entirely in the city of Niagara Falls. The road runs across the city in a northwest-southeast direction, following Hyde Park Boulevard from NY 384 in the east end of Niagara Falls to NY 104 in the town of Lewiston.

NY 77

NY 77 crosses from Genesee County to Niagara County north of the Tonawanda Indian Reservation. Within Niagara County, the route travels northwesterly across rural areas of Royalton to its north end at NY 31 east of the city of Lockport. NY 77 is known as Chestnut Ridge Road near NY 31 and Lewiston Road in the vicinity of the Genesee County line.

NY 78

NY 78 enters Niagara County from Erie County in the south as Transit Road, a major thoroughfare into the city of Lockport. The route intersects NY 93 just south of the city of Lockport, and finally in the city, the miles-long run of NY 78 as Transit Road comes to an end just past the NY 31 junction at the Erie Canal. North of downtown, the highway follows Lake Avenue northeast from Lockport through some rolling countryside. Commercial development returns about north of Lockport at Wright Corners, where the highway has a brief concurrency with NY 104. North of NY 104, NY 78 is known as Lockport–Olcott Road until it reaches its northern terminus at NY 18 in Olcott, a small hamlet on the shore of Lake Ontario.

NY 93

NY 93 begins in the center of the village of Youngstown at an intersection with NY 18F (Main Street). The route follows Lockport Street east from the junction, connecting to the Niagara Scenic Parkway at the eastern village line before proceeding in an east-southeast direction across the towns of Porter and Wilson. It continues on this track to Cambria, where the route turns eastward to run concurrent with NY 104 for to the Lockport town line. NY 93 leaves NY 104 at this point to follow Townline Road to the western edge of the city of Lockport.

At NY 31, NY 93 turns east, joining NY 31 on Saunders Settlement Road as it heads towards the city. The southward continuation of the road becomes NY 270. Just outside the city limits, NY 93 leaves NY 31 to run southward on the Lockport Bypass. It heads southeast and south across the southwest corner of the city along the bypass to its end at Robinson Road. From here, NY 93 turns east along Robinson Road, which changes names to Dysinger Road southeast of the city and to Akron Road in the town of Royalton. After becoming Akron Road, the route generally southeastward towards Tonawanda Creek and the Erie County line.

NY 104

NY 104 begins at NY 384 just east of the Rainbow Bridge in downtown Niagara Falls and heads north and east across the county on its way toward Rochester. From Niagara Falls, the route travels in north-northeasterly direction along the Niagara Gorge as it heads into Lewiston and connects to the Niagara Scenic Parkway and serves the Niagara Power Visitors Center, known as the Power Vista. Just north of the Power Vista, NY 104 meets I-190 at exit 25 via Upper Mountain Road (unsigned NY 954P). Continuing on, the highway has a junction with nearby NY 265 before descending the Niagara Escarpment toward the village of Lewiston. As the road heads down the ridge, it intersects the western terminus of NY 18 by way of an interchange.

Just east of the village limits, NY 104 connects to the Niagara Scenic Parkway one more time at the eastern terminus of NY 18F. The interchange is also the beginning of NY 104's run along Ridge Road. From here, NY 104 travels east through north-central Niagara County as Ridge Road. As the highway heads across the county, it briefly overlaps with NY 93 in Cambria and NY 78 in Wrights Corners. NY 104 leaves Niagara County at the southern terminus of NY 269, which runs along the Niagara–Orleans county line.

NY 148

NY 148 is a north–south route located entirely within northeastern Niagara County. It is named Quaker Road and runs from an intersection with NY 104 in Hartland to a junction with NY 18 in Somerset. NY 148 is maintained by Niagara County as part of CR 15.

NY 182

NY 182 runs across the city of Niagara Falls and the town of Niagara, connecting the Whirlpool Rapids Bridge to US 62 near the Niagara Falls International Airport. NY 182 is known by several names, the most prominent being Porter Road.

NY 265

NY 265 enters Niagara County as River Road, and shortly thereafter, joins NY 384 in North Tonawanda. The two highways run together along the Niagara River for to the eastern edge of Niagara Falls, where NY 265 breaks to the northwest to follow Military Road into the town of Niagara. As NY 265 heads northwest, it makes its way to the reservoir at the Niagara Power Project in the town of Lewiston, which it crosses while running alongside I-190. Shortly thereafter, access to I-190 and Canada is provided through Upper Mountain Road, which serves the last exit before the Lewiston–Queenston Bridge and the Canadian border. From there it is an equally short distance to NY 265's northern terminus at NY 104.

NY 269

NY 269 runs north–south along the Niagara-Orleans county line for its entire length and is called County Line Road. It runs north from an intersection with NY 104 at the community of Jeddo, passing through Millers and North Ridgeway on its way to a junction with NY 18 in the hamlet of County Line. The road also forms the boundary between the towns of Somerset and Hartland in Niagara County and the towns of Yates and Ridgeway in Orleans County.

NY 270

NY 270 is a north–south route in south-central Niagara County. It passes from Erie County to Niagara County by crossing over Tonawanda Creek (Erie Canal) and initially continues due north along Campbell Boulevard. About from the county line, the road bends northeastward toward the city of Lockport. It ends soon after at an intersection with NY 31 and NY 93 west of the city limits.

NY 271

NY 271 is a short north–south highway in eastern Niagara County. It serves as Middleport's Main Street, connecting NY 31 south of the village center to NY 104 in nearby Hartland. The section of NY 271 between NY 31 and the center of Middleport overlaps with NY 31E. In Middleport, NY 31E splits off onto State Street while NY 271 continues north to Hartland. The route is county-maintained as CR 45 from Mill Street (two blocks north of State Street) to the Middleport village line and CR 26 from the Middleport village line to NY 104.

NY 324

NY 324 officially begins at NY 384 in Niagara Falls and overlaps I-190 southward across the North Grand Island Bridge to Grand Island, Erie County. This section of NY 324 is not signed.

NY 384

NY 384 enters Niagara County as North Tonawanda's Main Street. Shortly thereafter, it joins NY 265 and becomes River Road as the two highways run along the Niagara River. The concurrency ends after , with NY 384 continuing along the riverside to provide the southernmost Niagara County exit for I-190. Past the freeway, NY 384 enters the city of Niagara Falls as Buffalo Avenue, intersecting NY 61 at the city line before veering onto Rainbow Boulevard at the eastern edge of downtown. After just one block, NY 384 turns north onto John B. Daly Boulevard at an intersection with the southern segment of the Niagara Scenic Parkway. The route runs along John B. Daly Boulevard to Niagara Street, where it turns west to access downtown Niagara Falls. NY 384 intersects the western terminus of NY 104 in downtown before ending at the eastern approach to the Rainbow Bridge.

NY 425