On postmortem examination, 2 geriatric captive male squirrel monkeys (Saimiri sciureus) were found to have pituitary masses that were unassociated with previous experimental manipulation. Both animals were euthanized due to apparently unrelated clinical reasons. Histopathology and immunohistochemical staining classified these tumors as thyrotrophic and corticotrophic pituitary adenomas. These cases represent the first reports of this tumor type in squirrel monkeys.