Pleural effusions may be related to pleuro-pulmonary or systemic disorders, including malignancy. Thoracentesis and thoracoscopy may be useful to diagnosis. In some cases, the diagnosis may be difficult and uncommon. We report the case of a hospitalized male for a pleuritis, with pleural effusion caused by a Bacillus megaterium infection, a Gram-positive, aerobic, spore-forming, and rod-shaped bacterium. To our knowledge, our case report is the first evidence of pleuritis due to B. megaterium. In the literature, up to now, B. megaterium infection has only been reported as involving the eye, skin, and brain.