BACKGROUND: Posterior disc displacement (PDD) of the temporomandibular joint (TMJ) is quite rare. The normal position of a disc is slightly anterior to the condyle, so the chances of disc displacement to the posterior direction are low. CASE PRESENTATION: A 71-year-old Japanese female reported with a chief complaint of lack of occlusion on the right-side molar teeth. Clinical examination revealed lack of occlusal contact in the right posterior region, nearly normal range of mouth opening (41.0 mm), masseter muscle tenderness, and deviation to the left on opening. MRI of the right TMJ showed PDD in both the open- and closed-mouth position and joint effusion. Conservative treatment with a non-steroidal anti-inflammatory drug, stretch exercise with fingers, and stabilization splint improved symptoms for 9 months. CONCLUSION: Conservative treatment was effective in managing the patient. A follow-up for 9 months with a repeat MRI was undertaken to monitor the progress.