It had been frequently reported that surgical trauma by implant surgery can be related with the onset of bisphosphonate-related osteonecrosis of the jaw (BRONJ). Recently, a long-standing dental implant itself has also been reported to be a risk for the development of BRONJ. This article reports a case of development of BRONJ after long-term oral bisphosphonate (BP) administration and successful maxillary sinus augmentation with a xenograft and simultaneous dental implantation. Considering that the dental implant at the grafted sinus had been maintained successfully for a long period, the BRONJ in the present case was not related to surgical trauma but was regarded a spontaneous onset. The current case highlights the necessity of a long-term follow-up for BP patients with maxillary sinus augmentation for implant placement, even though the short-term progress after sinus surgery is normally uneventful.