We report a case of heterotopic ossification of the maxillary sinus in a 30-year-old female who was treated surgically in our department. Heterotopic ossification (HO) refers to the formation of mature lamellar bone in nonosseous tissues. We present the radiographic and computed tomographic appearance, and discuss the surgical treatment, histopathologic results, and differential diagnosis. To the best of our knowledge, no other case of HO of the maxillary sinus has been reported yet.