A graying human population and the rising costs of healthcare have fueled the growing need for a sophisticated translational model of aging. Nonhuman primates (NHPs) experience aging processes similar to humans and, as a result, provide an excellent opportunity to study a closely related species. Rhesus monkeys share > 92% homology and are the most commonly studied NHP. However, their substantial size, long lifespan, and the associated expense are prohibitive factors. Marmosets are rapidly becoming the preferred NHP for biomedical testing due to their small size, low zoonotic risk, reproductive efficiency, and relatively low-cost. Both species experience age-related pathology similar to humans, such as cancer, diabetes, arthritis, cardiovascular disease, and neurological decline. As a result, their use in aging research is paving the way to improved human health through a better understanding of the mechanisms of aging.