Additive manufacturing (AM) is the process of fabricating three-dimensional physical models by layered manufacturing without the need of molds or dies. Surface finish of AM physical models is not satisfactory for most general engineering purposes. The aim of this study is to develop an acetone-vapor polishing system to smooth acrylonitrile butadiene styrene (ABS) parts fabricated by fused deposition modeling. Acetone vapor dissolved the outer surface of ABS parts and the surface roughnesses of ABS parts with complex geometries can be significantly reduced. The advantages of this system include flexibility to maintain dimensional accuracy, high polishing efficiency, low equipment costs, and no waste chemicals compared to conventional approaches.