Objective: Emergency departments and hospital emergency departments are important due to their critical role in providing urgent medical care to patients in dire need of medical interventions. Checking bottlenecks in new conditions and planning to reduce bed occupancy and hospitalization is needed. The purpose of this study is to investigate the relationship between the patient’s chief complaint and their departure to the emergency room. Methods: From non-traumatic patients referred to the emergency department of Imam Reza Hospital during 2018, about 57000 patients were selected and enrolled in the study. Then, age, sex, initial diagnosis, time of the final decision, and time of departure from the emergency department as well as hospitalization ward were included in the checklist. Patients whose documentation was incomplete were excluded. Data were entered into SPSS software version 15.0 and descriptive statistics (normal distribution, average of time, minimum time and maximum time, confidence interval, mode, and median, etc) were used for descriptive analysis and linear regression was used to analyze the correlation among findings. Results: There was a significant relationship between chief complaint and the length of stay in the emergency department (P = 0.046) and patients with dyspnea due to heart disease, bloody vomit, bloody stool, constipation, jaundice, anemia, decreased level of consciousness, diabetes, complications of diabetes, shortness of breath and kidney injury stayed longer in the emergency room compared to other complaints. Conclusion: The patient’s manner of expressing and chief complaint has an impact on the length of time they wait to leave the emergency room. Also, most patients with problems related to internal medicine have the longest time in the emergency room; in particular gastrointestinal patients have the longest stay in the emergency room.