The edentulous maxilla is often affected by bone resorption, sometimes making it difficult to place standard diameter implants. Narrow diameter implants made of titanium-zirconium (Ti-Zr) alloy, which has superior mechanical properties compared with titanium, have been proposed for these difficult situations. This retrospective clinical observation reports the outcome of the use of reduced diameter implants made of Ti-Zr alloy supporting maxillary overdentures retained with locator abutments. The charts of all patients who received maxillary overdentures supported by four unsplinted implants from January 2009 to June 2010 at the Department of Periodontology and Prosthodontics, Eastman Dental Hospital, Rome, Italy, were reviewed. All patients treated with four narrow diameter Ti-Zr implants were selected for the present case series. Ten patients were found, six of whom received augmentation procedures. After 12 to 16 months of follow-up, no implants were lost, and only one implant showed bone resorption greater than 1.5 mm. Implants showed a success rate of 97.5% and a survival rate of 100%. All prostheses were successfully in function. The present case series showed promising results regarding the use of narrow diameter implants made of Ti-Zr supporting maxillary overdentures retained with locator abutments.