This study is based on the basis of finalizing the diagnosis with echocardiographic findings in dogs with atrial fibrillation, which are considered likely to be thromboembolic. Dogs of the Golden Retrivier breed were admitted to the private korucan hospital for sterilization. The patients underwent a physical examination, echocardiography, electrocardiography and blood tests. During echocardiography, some patients were tachyarrhythmic, spontaneous echo contrast and mitral valve insufficiency were detected in the left ventricle and left atrium. As a result, it was concluded that echocardiography technique, supported by clinical examination, laboratory and ECG findings, is a standard diagnostic method for detecting thromboembolism in dogs.