Adrenarche is a developmental event involving differentiation of the adrenal gland and production of adrenal androgens, and has been hypothesized to play a role in the extension of the preadolescent phase of human ontogeny. It remains unclear whether any nonhuman primate species shows a similar suite of endocrine, biochemical, and morphological changes as are encompassed by human adrenarche. Here, we report serum concentrations of the adrenal androgens dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEAS) measured in 698 cross-sectional and mixed longitudinal serum samples from catarrhine primates ranging from 0.6 to 47 years of age. DHEAS in Pan is most similar to that of humans in both age-related pattern and absolute levels, and a transient early increase appears to be present in Gorilla. DHEA levels are highest in Cercocebus, Cercopithecus, and Macaca. We also tested for evidence of adaptive evolution in six genes that code for proteins involved in DHEA/S synthesis. Our genetic analyses demonstrate the protein-coding regions of these genes are highly conserved among sampled primates. We describe a tandem gene duplication event probably mediated by a retrotransposon that resulted in two 3-β-hydroxysteroid dehydrogenase/Delta 5-Delta 4 genes (HSD3B1 and HSD3B2) with tissue specific functions in catarrhines. In humans, HSD3B2 is expressed primarily in the adrenals, ovary, and testis, while HSD3B1 is expressed in the placenta. Taken together, our findings suggest that while adrenarche has been suggested to be unique to hominoids, the evolutionary roots for this developmental stage are more ancient.