Sinus augmentation has been shown to be an effective methodology to augment a deficient maxillary sinus. However, there are many techniques a clinician can choose from. Historically, lateral window or crestal osteotome approaches were the most frequently discussed techniques. In this paper, a sinus floor elevation technique with crestal window sinus elevation was proposed to treat cases of extremely atrophic maxillae (remaining bone height ≤ 2 mm). A crestal window is opened for the sinus membrane to be detached from the bony walls. After the proper elevation and membrane detachment, human particulated allografts were placed via the crestal access window to elevate the sinus membrane. Primary closure was then achieved, and after 6 to 9 months of healing, implant placement was performed. From the long-term clinical outcome that was obtained, the authors concluded that crestal window sinus elevation is a procedure with predictable outcomes for elevation of a maxillary sinus floor less than 2 mm thick, with an average elevation height of 11.73 mm.