The aim of this monographic was to collect the necessary information for the electrocardiographic evaluation of zebrafish, including anatomy, anesthesia, patient positioning, electrode location, and normal results in the electrocardiographic tracing of the fish. The monographic review was developed in three fundamental parts: I) The contextualization of the heart and its normal basic functioning in conventional species, the way in which its cells contract creating the functional syncytium and its electrical conduction system between cell and cell that allows the atria and ventricles to create the beats normally known as "Dup-Lup". II) Electrocardiography, understanding what the electrodes are, the amount located in a patient of the daily clinic such as canines and felines; the sense of the location of electrodes by their anatomy and the reading of the electrocardiographic tracing, understanding the leads taken in the frontal plane as D1, D2 and D3, as well as Avr, Avf, aVL and III) The variations found in the fish zebra, such as its anatomy, the reading of the waves, anesthesia and the recording method of the electrocardiogram in zebrafish (Danio rerio).