Purpose: The clinical evaluation of one-piece zirconia dental implants with different diameters to determine survival rate and type of implant failure. Materials and Methods: Information concerning implant surgery (number, diameter, length, and position of inserted implants; patient age, sex, risk factors, and bone quality) was extracted from the clinical records. All treated patients were then recalled for a follow-up examination to check the current clinical parameters concerning soft tissue, implants, and prosthetic reconstructions. Results: A total of 79 patients received 170 implants (diameter-reduced 3.25 mm: n = 59; diameter 4.0 mm: n = 82; diameter 5.0 mm: n = 29). The clinical examination showed no signs of gingival inflammation. Prosthetic information was available for 119 implants restored with single crowns (87 implants), fixed partial dentures (25 implants), and removable hybrid dentures (7 implants). Overall, 30 implants were lost due to lack of osseointegration (n = 17) or fracture (n = 13). The diameter-reduced implants showed the lowest survival rate (59.5%) compared to the implants with a diameter of 4.0 mm (90.6%) and 5.0 mm (73.9%). The survival rate for diameters of 3.25 mm was significantly lower than that for diameters of 4.0 mm. The estimated cumulative survival rate up to 3 years demonstrated a survival probability of 82.4% for all types of implant diameters and failure. Conclusions: Based on these results, diameter-reduced zirconia dental implants cannot be recommended for clinical use. The overall survival rate of 82.4% is not acceptable in comparison to the well-established survival rate of titanium implants.