Purpose: To investigate a computer-aided design/computer-aided manufacturing (CAD/CAM) process for producing one-piece removable partial dentures (RPDs) and to evaluate their fits in vitro. Materials and Methods: A total of 15 one-piece RPDs were designed using dental CAD and reverse engineering software and then fabricated with polyetheretherketone (PEEK) using CAM. The gaps between RPDs and casts were measured and compared with traditional cast framework RPDs. Results: Gaps were lower for one-piece PEEK RPDs compared to traditional RPDs. Conclusion: One-piece RPDs can be manufactured by CAD/CAM, and their fits were better than those of traditional RPDs.