Smooth muscle tumors of the serosal membranes are extremely rare and have received little attention in the literature. To the best of our knowledge, only 1 published series of 5 pleural smooth muscle neoplasms has been published to date. We describe a primary pleural neoplasm with smooth muscle differentiation documented by light microscopy, immunohistochemistry, and electron microscopy. This tumor originated in the parietal pleura in a 32-year-old white man and was diagnosed incidentally by chest radiography; the diagnosis was confirmed by magnetic resonance imaging and biopsy. Four years later, the tumor was noted to have increased in size and disseminated into the chest wall as a separate circumscribed mass located in the pectoral muscle. Both masses were resected and diagnosed as smooth muscle tumors. We conclude that smooth muscle tumor of the pleura is a well-defined entity with a low, but definite malignant potential; therefore, we recommend complete resection and long-term follow-up for all patients.