Diaphragm disease (DD) is an uncommon gastrointestinal abnormality typical of nonsteroidal anti-inflammatory drug (NSAID)-induced injury. DD of the small intestine is well defined in its gross appearance (multiple circumferential stenosing lesions); however, its histologic features have been studied in few cases. To better define and update the histologic features of DD, we describe 10 cases in which patients underwent resection of portions of small intestine for DD. Selected gross features and 12 microscopic features were assessed. The typical gross appearance of DD was associated with focal chronic injury of the mucosa with mild to moderate inflammatory infiltrate. A wide array of additional abnormalities was found: eosinophilic enteritis (3 cases), inflammatory fibroid polyp (1 case), enteritis cystica profunda (1 case), villous atrophy (1 case), and neuromuscular and vascular hamartoma-like changes (9 cases). DD and, therefore, NSAID-related injury, should be considered in the differential diagnosis of several conditions affecting the small intestine.