Route 33 begins at an interchange with the Trenton Freeway (US 1) and the northern terminus of Route 129 in the state capital of Trenton, Mercer County. The route heads southeast on Market Street as a four-lane divided highway, passing over NJ Transit's River Line and Amtrak's Northeast Corridor, just south of Trenton Transit Center. After intersecting Clinton Avenue, Route 33 becomes Greenwood Avenue and heads east as a two-lane road through residential neighborhoods on the east side of the city, passing north of Trenton Central High School and serving a few small businesses. Greenwood Avenue then enters Hamilton Township and enters a slightly more commercialized area before passing north of a cemetery. At this point, Greenwood Avenue ends, and Route 33 merges with Nottingham Way and becomes a four-lane boulevard lined with many homes and businesses. After reaching a modified interchange with Interstate 295 (I-295), Route 33 turns right off of Nottingham Way and becomes a two-lane road with a center left-turn lane. The route passes many business and crosses through a wooded residential area before coming back into a commercial area and entering Robbinsville Township, where Route 33 turns northeast onto US 130 and the two routes run concurrently on a four-lane divided highway.