BACKGROUND: Nowadays, due to widespread usage of anti-pain drugs, more attention is being paid to tramadol, although it has only been recognized  rather recently in veterinary medicine. Therefore, evaluation of its effects on various organs is a principal issue. OBJECTIVES: The aim of present study was to investigate cardiac function change following administration of tramadol using electrocardiography and echocardiography. METHODS: Five healthy dogs aged 3-5 years and weighting 20-26 kg were selected for study. To check the health of animals, clinical and laboratory examinations were performed. Then animals were kept for 2 weeks and vaccination and anti parasite therapy were prescribed for them. This study was conducted in 3 stages and ECG and echocardiography were recorded: before tramadol injection, immediately after injection and one hour after that. Parametric data analysis of variance with repeated measure was conducted using SPSS version 20. RESULTS: Along evaluated parameters, only left ventricular volume in end-diastole and end-systole, time interval between the Q wave to aortic valve closure, stroke volume and ejection fraction showed significant difference between the three stages. CONCLUSIONS: In conclusion, tramadol shows remarkable anti-pain effects with low cardiac side-effects in comparison to other opioid drugs. However, more studies are needed due to the importance of this subject.