The route passes through many communities along the way, including New Brunswick, Highland Park, Edison, Metuchen, Rahway, and Elizabeth.

Route 27 is a two- to four-lane undivided highway for most of its length, passing through a variety of urban and suburban environments.

Route 27 crosses the Raritan River on the Albany Street Bridge, which connects Highland Park on the east with New Brunswick on the west.

Route 27 runs parallel to Carnegie Lake, then crosses over the Millstone River just north of the historic Kingston Bridge.

It continues northeast through a mix of woodland and residences, intersecting with Promenade Boulevard, which heads east and becomes CR 522 after crossing US 1.

The route continues north to an intersection of Gateway Boulevard (CR 518), where it resumes its northeast direction and heads into Kendall Park as a variable two- to four-lane road, entering denser suburban development.

Past that intersection, Route 27 forms the border of Franklin Township to the west and North Brunswick to the east, passing through suburban development with some areas of farmland, seeing about 38,487 cars a day.

[1][2] The road forms the border of Franklin Township and New Brunswick upon intersecting with How Lane (CR 680) becoming four-lane Somerset Street.

Past this intersection, the route becomes a two-lane street that heads into Downtown New Brunswick, south of the main campus of Rutgers University.

[1] Route 27 resumes heading northeast past this intersection as a four-lane road that passes by homes, entering Edison, where the name changes to Lincoln Highway.

[1] Beyond this interchange, Route 27 crosses into Metuchen and becomes two-lane Essex Avenue, which turns to the east and heads through residential areas.

[2] The route closely parallels the Northeast Corridor rail line and crosses into Woodbridge, widening to four lanes at this point.

At the intersection of Wood Avenue (CR 617), Route 27 forms the border of Roselle to the west and Linden to the east, with about 23,081 vehicles using the road on a daily basis The route crosses the inactive Rahway Valley Railroad line that is owned by the Staten Island Railway.

[3] Past the one-way pair, Route 27 resumes east on four-lane Westfield Avenue, turning north onto Broad Street.

Route 27 continues north, passing under railroad tracks carrying Conrail Shared Assets Operations' Lehigh Line and NJ Transit's Raritan Valley Line and crossing Conrail Shared Assets Operations' Poinier Street Lead line/Irvington-Hillside Industrial Branch at-grade, before it comes to an intersection of Poinier Street, where the route heads east along that road to its northern terminus at an interchange with McCarter Highway (Route 21) and Broad Street.

[5] Route 27 follows portions of several 19th-century turnpikes, including the Essex and Middlesex Turnpike, which was chartered on March 3, 1806, to run from New Brunswick to Newark along what is today Route 27, the Northeast Corridor rail line, and Broad Street in Newark, the Georgetown and Franklin Turnpike, chartered on February 15, 1816, to run from Lambertville to New Brunswick along the present-day alignments of CR 518 and Route 27, the Newark and Elizabeth Plank Road, chartered on March 14, 1856, and the Princeton and Kingston Branch Turnpike, chartered on December 3, 1807, to run from Trenton to Kingston along current CR 583 and Route 27.

[13] In the 1953 New Jersey state highway renumbering, the southern terminus of Route 27 was cut back to Princeton to avoid the concurrency with US 206.