Obesity is one of the most frequent nutritional problems in dogs. It has been associated with some comorbidities and reduction in quality of life. The obese dog is in great risk of developing chronic health problems, such as cardiovascular disturbances. Obesity is associated with a wide variety of electrocardiographic abnormalities, including arrhythmias, which can be attributed to structural and hemodynamic cardiac abnormalities and to fatty infiltration of the conduction system. The aim of this study was to evaluate the heart rhythm and heart rate by computerized electrocardiographic in obese dogs. Thirty-eight obese dogs were submitted to computerized electrocardiographic using the TEB ECGPC® (TEB) system. Dogs were positioned in right lateral recumbency and the electrode clips were attached to the animal's skin in the standard positions as described by Tilley (1995). The speed was 50 mm/sec and the electrocardiogram (EKG) was standardized at 1 mV = 1 cm. The EKG analysis was obtained from lead II. Most dogs (81.6%) showed normal heart rhythm. However, in 18.4% of dogs, changes were observed. Sinus arrhythmia was the predominant cardiac rhythm, obtained in 44.8% of dogs. Sinus rhythm was observed in 36.8%, sinus bradycardia in 8%, sinus tachycardia in 2.6%, sinoatrial block in 2.6%, premature ventricular complexes in 2.6%, and first-degree heart block in 2.6% of obese dogs. The average heart rate was 115.1 ± 28.2 beats per minute. In conclusion, obese dogs should be evaluated periodically. Thus, possible cardiac abnormalities, like cardiac arrhythmias, can be recognized and treated early.