Thoracic Radiology is a diagnostic technique used to study several aberrations, including cardiac abnormalities, which can be determined by VHS (vertebral heart size). The heart length and width are measured, and the CTR (cardiothoracic ratio) is calculated, by comparing the heart width to the thoracic diameter. This study aimed at measuring the cardiac silhouette of non-human primates (PNH) belonging to the genus Sapajus sp., and the Alouatta guariba species through VHS and CTR. From among the eight animals assessed, it was evident that in both the Sapajus sp. and the Alouatta guariba, the highest HSV change index was observed, depending upon the age of the animal. However, although the individuals of the Alouatta guariba species are bigger in size and heavier, the animals of the genus Sapajus sp. have a larger heart size in proportion to their body.