Displacement of an implant into the maxillary sinus is a rare complication in dental implant clinical practice. This complication mainly arises due to an inadequate bone height and peri-implant infection. The presence of a foreign object, such as an implant, in the maxillary sinus causes sinusitis via impaired mucociliary flow and foreign body reactions. Therefore, foreign object in maxillary sinus must be removed. Caldwell–Luc surgery may be performed to remove foreign bodies and lesions from the maxillary sinus. Herein, we describe the case of a patient whose dental implant slipped into the right maxillary sinus during the insertion of the healing cap due to periimplant infection and removal of the implant via an intraoral Caldwell–Luc surgical approach. The intraoral Caldwell–Luc surgery technique proved to be a safe, reliable method for the removal of a foreign object from the maxillary sinus.