 NY 343 begins at an intersection with NY 82 (cosigned as U.S. Route 44 or US 44 until 2008) in the hamlet of South Millbrook, located within the village of Millbrook. The road heads eastward into the town of Washington, intersecting an old alignment of NY 82 and passing to the south of Millbrook Golf and Tennis Club. NY 343 continues past fields, residential homes, and farms. The highway passes south of the creek, Mill Brook, entering the hamlet of Littlerest, where it turns to the southeast at an intersection with County Route 99 (CR 99). At the intersection with CR 23, NY 343 again changes direction, this time to the northeast, and soon crosses Stone Church Brook in the hamlet of Mutton Hollow. Here, NY 343 changes directions a third time, traveling to the southeast once again towards the hamlet of Dover Plains.
