Purpose: The aim of this case report is to present the successful clinical treatment of two cases of postoperative infection following maxillary sinus augmentation. Methods: In the two cases of postoperative infection, immediate total removal of the grafted material from the sinus was conducted to stop the spread of the infection, after which a high dose of antibiotics was administrated. Re-augmentation procedures were then conducted after the infection subsided. Results: No further complications occurred after sinus re-augmentation. The dental implants placed in the re-augmented sinus were clinically osseointegrated, and the implant-supported restorations in the two cases of postoperative infection have been functioning very well for over 2 years. Conclusions: In the case of infection of the grafted sinuses, it is necessary to completely remove the graft materials and then administer a high dose of antibiotics to treat the acute infection, after which sinus re-augmentation is suggested.