Objective: The present study aimed to investigate the effectiveness of copeptin levels in detecting increased pulmonary artery pressure and right ventricular dysfunction in patients with acute pulmonary embolism. Methods: A total of 116 patients who presented to the emergency department with chest pain or dyspnea and were diagnosed with acute pulmonary embolism and 30 healthy controls were included in the study. Plasma copeptin levels of patients and healthy control group were measured. Right ventricular functions and pulmonary artery pressures were evaluated in echocardiography of patients diagnosed with acute pulmonary embolism. Results: Copeptin levels were significantly higher in patients with right ventricular dysfunction than in those without right ventricular dysfunction [median 1.06(0.03-7.14) vs. 0.59(0.31-2.50), p= 0.01]. Conclusion: Copeptin can be used as a new biomarker in the diagnosis of acute pulmonary embolism and in predicting right ventricular dysfunction and increased pulmonary artery pressure in patients with acute pulmonary embolism.