This study aimed to detect the incidence, etiology, risk factors, and severity of nosocomial diarrhea among adult inpatients in a medical ward in Iraq. The study was conducted among patients admitted to the medical ward from June 1, 2019, to January 31, 2020, in AL-Sader medical city. The surveillance for nosocomial diarrhea was performed by monitoring every patient in the ward 3 times/week. 1050 patients were admitted to the medical ward in AL-Sader medical city. Of these, 52 patients (mean age 58±12.91 years, range 32 to 80) developed new-onset diarrhea during hospitalization. There was a significant relationship between the severity of diarrhea and age, residence, antibiotic use, including number and duration of antibiotics, immunosuppressive agents (steroids/chemotherapy), duration of hospital stay, level of consciousness, and enema use. Nosocomial diarrhea is a significant clinical problem that complicates about 5% of all admission in the medical ward. Various microorganisms account for nosocomial diarrhea, including E. histolytica, G. lamblia, and Candida. Several risk factors associated with the severe form of nosocomial diarrhea include old age, antibiotic use, immunosuppressive use, and length of hospital stay.