Introduction: The rehabilitation of areas with localized horizontal atrophy in the molar region or with reduced interdental spaces using dental implants is challenging. In many cases, horizontal regeneration must be performed prior to implant placement, which increases the morbidity of the procedure, particularly considering it involves a unitary implant. For these situations, narrow-diameter implants with reduced platforms offer a viable solution to address localized atrophies successfully. This case series demonstrates situations resolved with these implants in a safe and predictable manner. Materials and Methods: Narrow implants with a diameter of 3.3 mm and a narrow platform (3.0 mm) were prospectively analyzed. These implants were placed in molar positions and rehabilitated as single-unit restorations in cases of localized horizontal atrophy with reduced mesiodistal spaces, avoiding the use of regenerative techniques to restore lost width. The primary variable evaluated was implant survival, followed by crestal bone loss and the occurrence of surgical or prosthetic complications during the follow-up period. Qualitative variables were described using frequency analysis, while quantitative variables were summarized using mean and standard deviation. Implant survival was estimated using the Kaplan-Meier method. Results: Thirteen patients were recruited, receiving a total of 15 implants that met the inclusion criteria. Of these, 73.3% were placed in the mandible, with position 46 being the most frequent location. All the implants studied had a diameter of 3.3 mm with a platform of 3.0 mm and were placed for unitary molar rehabilitation, using screw-retained crowns supported by single abutments. Implant lengths were 5.5 mm in 33.3% of cases and 6.5 mm in the remaining 66.7%. The mean mesial bone loss at the end of the follow-up was 0.49 mm (+/- 0.21), while the mean distal bone loss was 0.43 mm (+/- 0.28). Conclusions: Narrow-platform (3.0 mm) and reduced-diameter implants can be placed in molar regions and rehabilitated as single-unit restorations in cases of localized horizontal atrophy, reduced interproximal spaces, or both factors combined, with favorable outcomes.