Background: Length of stay is an important performance indicator for hospital management and a key measure of health care efficiency. This paper aims to determine the average length of stay in our center and the factors that influence it. We also investigate whether our hospital's length of stay is a key performance measure that can be used to design quality improvement initiatives. Methods: We performed a retrospective analysis of hospitalizations at the Multi-disciplinary Internal Medicine Department of King Abdulaziz University Hospital, Jeddah between 2010 and 2013. We collected data including demographics, admitting diagnosis, admitting unit, treatments administered, and history of transfer from the Intensive Care Unit. Results: The mean length of stay was 5.9 (6.8) days. Patients admitted through the Emergency Department were more likely to have a longer hospital stay compared with those admitted through Day Care or the Outpatient Department (P < 0.001). Expatriates (P < 0.001), bedridden patients (P = 0.02), and those who received prophylaxis for deep venous thrombosis (P < 0.001) were more likely to have a longer length of stay than the rest of the sample. Furthermore, patients admitted in the morning hours had a significantly shorter length of stay than those admitted in the evening hours (P < 0.001). Conclusion: The length of stay among patients at our department is affected by hospital- or patient-specific factors. Health care can be improved by identifying and monitoring the length of stay in high-risk patients.