Purpose: The purpose of this prospective randomized clinical trial was to test the hypothesis that narrow-diameter titanium-zirconium (Ti-Zr) alloy implants with a chemically modified hydrophilic surface are not inferior in regard to crestal bone level change compared to standard-diameter implants with the same implant surface and material. Materials and Methods: This multicenter study included 50 patients in need of a single tooth replacement in the anterior (canine to canine) or premolar region of the mandible or maxilla. Patients were included if the site could accommodate a 4.1-mm-diameter implant. Implants were temporarily restored at 3 to 4 weeks after placement. Definitive restorations were delivered 4 to 6 months after placement. Patients returned 1 year after implant loading for clinical measurements and radiographic examination. The primary outcome was mean crestal bone level changes measured between implant loading and 12 months postloading. Secondary outcomes included implant success, survival, gingival recession, and patient satisfaction. Results: Fifty patients were enrolled; 47 completed the study. Twenty-three patients were in the narrow-diameter implant group (test), and 24 patients were in the standard-diameter implant group (control). The success and survival rates at 12 months postloading were 100% for both groups. The change in the mean crestal bone level from implant loading to 12 months postloading around narrowdiameter implants was -0.27 ± 0.34 mm. For the standard-diameter implants, the change was significantly higher at -0.48 ± 0.67 mm (P = .02). No significant difference was found in gingival recession and patient satisfaction. Conclusion: The results of this prospective randomized clinical trial suggest noninferiority of the narrow- vs standard-diameter Ti-Zr implant. In addition, bone remodeling was less pronounced for the narrow-diameter implants. Keywords: dental Implant, marginal bone level, prospective study, randomized clinical trial, single implant, soft tissue