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Background In sinus augmentation, when remaining bone height is ≤5 mm, a lateral window approach is often the preferred choice; nonetheless, patients prefer to have a less invasive approach such as crestal sinus augmentation (CSA). Prior case reports have described the use of various staged approaches of a CSA technique in cases of limited bone height. The aim of this report was to describe the results of a case series in which a two‐stage CSA technique was used in patients with 4 to 6 mm of bone height. Methods Nineteen subjects with 28 sinuses of initial vertical bone height of 4 to 6 mm were included in which a two‐stage CSA technique was used in place of a lateral window approach. In the first surgery, 0.3 mL graft material was inserted into all sites. In the second surgery, 13 sites were filled with 0.2 mL graft material and remaining 15 sites were filled with 0.4 mL. Results No damage was observed in the maxillary sinus floor membrane after first 0.2 mL filling; however, one case had Schneiderian membrane perforation after filling 0.4 mL. The average elevation height (EH) after first surgery was 5.81 ± 0.7 mm, 5.15 ± 0.91 mm before second surgery, 6.69 ± 0.89 mm with 0.2 mL filling (total 0.5 mL) and 8.11 ± 1.24 mm with 0.4 mL filling (total 0.7 mL). The thickness of maxillary sinus membrane before first surgery was 2.6 ± 2.59 mm; however, it has become 0.97 ± 1.59 mm before second surgery, with a decrease of 1.6 mm estimate. Conclusion This case series that assessed outcomes of staged crestal maxillary sinus augmentation was an effective approach to elevating 6 or 8 mm alveolar bone height without causing major membrane perforation. However, the two‐stage approach was used in the limited residual bone height (4 to 6 mm) and required two separate surgical procedures.