Purpose: Sinus floor elevation (SFE) and simultaneous implant placement is predictable and reproducible. However, the graft material for the antral cavity remains a topic of debate. Considering the high osteogenic potential of the sinus membrane, most graft materials are generally accepted. This study aimed to assess the outcome of simultaneous SFE and implant placement, using leukocyte- and platelet-rich fibrin (L-PRF) as a sole graft material. Materials and Methods: This study was designed as a single cohort prospective study. Clinical and radiographic measurements (cone beam computed tomography [CBCT]) were performed immediately after implant placement and at abutment connection (6 months later). The amount of newly formed bone was linearly recorded on cross-sectional images. Four measurements (mesial, distal, buccal, palatal) were registered with the axis of the implant as reference. Results: Six lateral and 22 transalveolar SFEs were performed in 26 patients with simultaneous implant placement. Six months after surgery, 27/29 implants were clinically integrated. The mean vertical bone gain was 3.4 ± 1.2 mm and 5.4 ± 1.5 mm for transalveolar SFE and lateral SFE, respectively. The level of the new sinus floor was in all cases in continuation with the apex of the implant, and the peri-implant crestal bone height was stable. Conclusion: L-PRF as a sole graft material during simultaneous SFE and implant placement proved to be a practical, safe, and economical subsinus graft material, resulting in natural bone formation.