Purpose: The purpose of the present case report was to document a maxillary sinus floor augmentation procedure involving ligation of a blood vessel with a nearly 3-mm diameter in the lateral wall of the maxillary sinus. Materials and methods: A bilateral maxillary sinus floor augmentation procedure was performed in a 51-year-old healthy man. The preoperative computed tomography scan revealed a bony canal within the lateral maxillary sinus wall of the right as well as the left side close to the alveolar ridge. Results: A vessel with a diameter of nearly 3 mm was identified during the sinus floor augmentation on the left side. The vessel was exposed and ligated. A vessel with a diameter of approximately 1 mm was identified on the right side and the sinus floor augmentation was performed without ligation. No complications were observed and the postoperative healing was uneventful. Conclusions: Although accidental laceration of vessels with an unusually large diameter during maxillary sinus floor augmentation is not life-threatening, impaired visualisation may compromise the augmentation procedure, including the elevation of the Schneiderian membrane. Moreover, postoperative bleeding and formation of a haematoma may occur. Therefore, ligation of vessels with an unusually large diameter is recommended during maxillary sinus floor augmentation to minimise intra- and postoperative complications.