The objective of this study is to evaluate the electrocardiographic findings in naturally infected horses by trypanosomiasis as well as to investigate the presence of Trypanosoma sp. in northern Iraq. Twenty-two male horses aged 3-7 years and their weights of 340 to 390 kg were examined. All infected horses showed anaemia, also two horses died, with clinical signs suggestive of heart failure. Results showed trypanosomes in blood smears of infected horses, which was confirmed using the conventional polymerase chain reaction (c-PCR) technique. 12 horses (54.54%) are infected of them 7 (31.82%) were infected with T. evansi and 5 (22.72%) were infected with T. vivax. Clinical, haematological, and electrocardiographic evaluations (ECG) were performed. Serum cardiac troponin (cTnI) biomarker was measured to support ECG findings and a deeper understanding of myocardial tissue damage, and the results were compared with normal values in healthy horses and were found negative for blood smear and PCR. The electrocardiograms showed significant changes which characterized by the length of the P and T waves and the QRS complex in addition to the deviation of the electrical heart axis to the left and tachycardia. The mean values of serum cTnI were significantly higher in T. evansi and T. vivax of infected horses (0.78 and 17.5 ng/m respectively) compared to healthy horses (0.01 range 0.01-0.03 ng/mL). T. evansi and T. vivax are responsible for the incidence of heart lesions, which are associated with heart failure, changes in the electrocardiogram, and death of the affected horses.