Purpose: To investigate the long-term predictability of simplifying mandibular overdenture treatment using single-stage surgery and immediate prosthetic loading of a single implant to provide a more affordable treatment option. Materials and Methods: A total of 29 patients with a mean age of 68 years with problematic mandibular dentures were treated. A single implant (Brånemark System Mklll TiUnite, Nobel Biocare) was placed into the mandibular midline for primary stability. A ball attachment was placed, and the retentive cap was incorporated into the existing denture. The patients were recalled at 3 and 12 months and at 3, 5, 10, and 15 years. Clinical assessments, radiographs, and resonance frequency analysis were recorded. All complications, failures, maintenance, and reasons for failure to follow-up were noted. Visual analog scale (VAS) questionnaires were used to record patient satisfaction (ANOVA; P < .05). Results: One implant did not achieve sufficient primary stability to be immediately loaded and was treated with a two-stage delayed loading protocol. Of the 28 patients receiving immediately loaded implants, 14 patients were available for follow-up at 15 years. Implant survival remained at 100% throughout the study. Patient satisfaction was high, with a significant increase in all comfort and functional parameters (P values ranged from < .001 to .07) throughout the 15-year period. Conclusions: These 15-year results indicate that immediate loading of a single oxidized surface implant used to retain a mucosa-borne overdenture is a safe, reliable, and cost-effective treatment with high levels of patient satisfaction long term.