Overuse of emergency rooms (ER) is a public health problem. To investigate this issue, a cross-sectional survey was conducted at the ERs of King Abdul-Aziz Hospital, King Fahd Hospital, and Al-Thaghor Hospital in November 2013 with the aims of estimating emergency service utilization for non-urgent cases, identifying the predictors of ER utilization for non-urgent cases, and measuring patients' knowledge of primary healthcare centers (PHCCs). Patients were interviewed using a structured questionnaire and the data were analyzed using the Statistical Package for the Social Sciences. We recruited 300 patients; males comprised 50.7% of the sample. A higher proportion of patients with non-urgent cases visited the ER three to four times a year (P=0.001). A higher proportion of patients without emergencies had not attempted to visit an outpatient clinic before the ER (P=0.003). Most patients without emergencies thought the ER was the first place to consult in case of illness. Most patients who visited the ER were single, <15 years, and had lower incomes. Patients requested ER services for primary care-treatable conditions because of limited services and resources as well as limited working hours at PHCCs. Most patients (90.0%) were knowledgeable about PHCCs, with those of lower education being more knowledgeable. Patients reported long ER waiting times (≥3 hours), no organization (85.9%), and lack of medical staff. Overall, overuse of ER services is high at the Ministry of Health hospitals in Jeddah. The risk factors for ER overuse are age<15 years, singlehood, and low incomes. Policy makers and health providers have a challenging task to control ER overuse. We recommend developing strategies to implement policies aimed at reducing non-urgent ER use as well as making healthcare services more available to the population.