PA 233 begins at an intersection with PA 997 in the borough of Mont Alto in Franklin County, heading east on two-lane undivided Park Street. The road passes homes, becoming the border between Quincy Township to the north and Mont Alto to the south before fully entering Mont Alto again. The route heads entirely into Quincy Township as it passes the Penn State Mont Alto university campus. From here, PA 233 becomes Mont Alto Road and continues near Mont Alto State Park and heads into Michaux State Forest. The route turns northeast to ascend Rocky Mountain, a part of the South Mountain range, becoming an unnamed road. The road enters Guilford Township and makes a hairpin turn to the south to descend the mountain, crossing back into Quincy Township. PA 233 curves east before heading northeast through more forests and entering Guilford Township again, where it crosses the Appalachian Trail. The route turns north-northeast onto Rocky Mountain Road and runs through more mountainous areas, heading into Greene Township. Here, PA 233 passes through Caledonia and crosses US 30 before running through forested Caledonia State Park as an unnamed road, turning northeast.