Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This work was supported by “Instituto de Salud Carlos III” and “Fondos Europeos de Desarrollo Regional FEDER” (grant numbers PI20/00637 and CIBERCV16/11/00486) and Conselleria de Educación – Generalitat Valenciana (PROMETEO/2021/008). Introduction The His bundle is responsible for transmitting the electrical impulse from the atria to the ventricles where it connects with the Purkinje cells in both normal and abnormal hearts. The aim of this study was to perform a morphometric analysis of His bundle characteristics of in humans, dogs, horses and pigs and compare them in these studied species. Methods We analyzed five hearts of human male adults, five male pig hearts, five hearts from male horses and five hearts of male dogs. Histological sections of 5 μm thickness were obtained and stained with hematoxylin–eosin and Masson’s trichrome; the desmin and periodic acid–Schiff methods were also used for precise identification of cells. Results The His bundle was found to be longer in horses (2.85 ± 1.02 mm) and pigs (1.77 ± 0.9 mm) than in dogs (1.53 ± 0.8 mm) or humans, in which it was shortest (1.06 ± 0.6 mm). The area and diameters in His bundle cells, were significantly larger in pigs and horses than in humans (p < 0.001) or dogs (p < 0.001). We found two organizational patterns of His bundle components: group I, with large cells and a high amount of collagen fibers in ungulates (pigs and horses); and group II, with smaller cells and lower abundance of collagen fibers in humans and dogs. Conclusions Determining morphometrically cell size variations in the His bundle allows us not only to identify this bundle by histological or anatomical location but also to differentiate these cells from others such as nodal or Purkinje cells. Our analysis revealed that His bundle cells have discrete identities based on their morphometric and histological characteristics.