The subcarapacial vessel is a popular site for venipuncture and intravenous medication administration in chelonians. Reports of adverse effects when using this site have increased, prompting evaluation of its safety. This study aimed to evaluate the anatomy of the subcarapacial vessel in 25 individual chelonians (2 box turtles, 3 red-eared sliders, and 20 red-footed tortoises) using computed tomography (CT). Individuals were sedated and administered contrast in the subcarapacial vessel. The vessel was visualized in 50% of the box turtles and red-footed tortoises, and 100% of the red-eared sliders. All species had contrast extravasation in the subarachnoid space, with red-footed tortoises having the largest percentage (70% compared to 50% and 33% of box turtles and red-eared sliders, respectively). Extravasation of contrast in the trachea or bronchi (70%) and lungs (80%) was seen in the red-footed tortoises only. Higher prevalence of contrast extravasation in the red-footed tortoises is likely because of anatomical differences, including a more cranially extending lung field and domed-shaped carapace compared to the other species. These findings highlight the risk associated with using the subcarapacial vessel for intravenous medication administration in certain species of chelonian.