Malakoplakia is a rare, chronic inflammatory condition characterized by defective macrophage function. The majority of cases involve the genitourinary tract, but isolated cases have been reported from other organ systems including one prior report involving the maxillary sinus. We present a case of malakoplakia expanding the frontal and ethmoid sinuses mimicking a mucocele at presentation. The diagnosis was made at the time of surgery based on the histopathologic finding of von Hasemann cells and Michaelis-Guttmann bodies. Sinus-specific clinical aspects will be discussed including diagnostic and treatment considerations. Laryngoscope, 2009.