(1) Background: In dentistry, a reduction in surface roughness is established mostly by conventional mechanical polishing to hinder biofilm adhesion. This is time- and labor-intensive. Plasma electrolytic polishing is believed to be an effective finishing method due to the reduced treatment time and materials used for applications in dentistry. (2) Methods: Co-Cr-Mo dental alloy samples were sandblasted and prepared with either plasma electrolytic or conventional mechanical polishing. Evaluation of the polishing methods was obtained by atomic force microscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. (3) Results: The sandblasted samples showed the highest surface roughness (Heraenium® Sun 991 ± 288 nm; Wironit® 1187 ± 331 nm). Our results show that with plasma electrolytic polishing, Co-Cr-Mo surfaces can be polished with a surface roughness in the nanometer range, comparable to those achieved by conventional mechanical polishing. Conventional mechanical polishing (Heraenium® Sun 134 ± 23 nm; Wironit® 114 ± 11 nm) provided lower surface roughness values compared to plasma electrolytic polishing (Heraenium® Sun 288 ± 94 nm; Wironit® 261 ± 49 nm). We anticipate our pilot study as a starting point for future studies to refine process parameters and quantitative microbiological assays. (4) Conclusions: Plasma electrolytic polishing might have a promising future for polishing dental alloys.