The purpose of this study was to introduce our patient-specific bioactive porous titanium implant manufactured using selective laser melting (SLM) and to establish the efficacy and safety of the implant for stand-alone anterior cervical discectomy and fusion (ACDF) based on a prospective clinical trial. We designed a customized ACDF implant using patient-specific data and manufactured the implant using SLM. We produced a bioactive surface through a specific chemical and thermal treatment. Using this implant, we surgically treated four patients with cervical degenerative disc disease and evaluated the clinical and radiological results. We achieved successful bony union in all but one patient without autologous bone grafting within 1 year. We observed no implant subsidence during the follow-up period, and all clinical parameters improved significantly after surgery, with no reported implant-related adverse effects. Our customized bioactive porous titanium implant is a safe and promising implant for stand-alone ACDF.