Introduction: Mushroom extracts are used, mainly due to immunomodulatory and antitumor proprierties. Among the general and species is the Agaricus brasiliensis or SunMushroom. However herbal remedies can cause changes in morphology and functionality of various organs. Therefore, these reporters need to be analyzed for applicability of this compound. The aim of the present study was to analyze the structural characteristics of the heart of Swiss mice employing light microscopy and scanning electron microscopy methods. Materials and methods: Swiss mice were used, divided into 2 groups: Control (n=6) and Agaricus brasiliensis (n=6), and the second group treated with the extract daily. After 60 days, under anesthesia withdrew from the samples, which were submitted to histological routine for obtaining serial sections. Results: Microscopic analysis revealed the aspects of the heart of Swiss mice: The formation of layers (epicardium, myocardium and endocardium) with partial view of the papillary muscles. Using the technique of Picro-Sirius: In yellow, the muscle fibers; in red, collagen fibers. Under polarized light, show the types of collagen fibers in red and green, significant collagen type I and III respectively. Conclusion: The arrangement of muscle fibers and collagen did not vary between the two groups.