The computerized electrocardiography has been used in cardiology as an auxiliary method of diagnosis presenting a high degree of reliability. However, studies show differences related to the amplitude and duration of some deflections of the electrocardiogram between conventional and computerized methods, so we should consider these differences when interpreting results. This experiment aimed to compare conventional and computerized electrocardiography in 76 dogs - mongrel, healthy, of both sexes. Electrocardiograms were carried out simultaneously in both the methods (in derivation II, speed of 50 mm/sec, 1 cm = 1 mV). It was analyzed heart rate (HR) and rhythm, measurement of waves and intervals. We used the chi-square test and ANOVA. The level of significance was set at 5%. The results showed that HR did not differ between the methods used and the duration of the PR interval did not range among them. The duration of the P wave in the conventional method was 0.037 ± 0.007 (ms), while the computerized method showed values from 0.048 ± 0.038 (ms) (p < 0.014). The same overestimation was observed in QT interval, in which computerized method gave an interval of 0.184 ± 0.019 (ms) and the conventional resulted in an interval of 0.169 ± 0.021 (ms) (p < 0.001). Regarding the R wave amplitude, the conventional method gave higher values (1.46 ± 0.51 mV) than the computerized (0.95 ± 0.37 mV) (p < 0.001). The cardiac rhythm was constant in both methods, prevailing sinus rhythm. In general, the computerized method overestimated the duration and amplitude of waves and electrocardiographic ranges, except the R wave amplitude that appeared higher in conventional method.