Aging of the human testis and associated cellular changes are difficult to assess, thus we used a translational non-human primate model to get insights into underlying biochemical processes. Using proteomics we analyzed testicular tissue of six young (age 2 to 3) and four old (age 10 to 12) C. jacchus individuals. Mass spectrometry identified 63124 peptides, which could be assigned to 5924 proteins. Among them we found proteins, which are specific for germ cells, Leydig cells, and somatic cells, indicating the relevance of the dataset. The quantitative analysis showed 31 differentially abundant proteins, of which 29 proteins were more abundant in old animals. An increased abundance of several anti-proliferative proteins, among them CDKN2A, indicate slowed cell proliferation in older testes. Immunohistochemistry localized CDKN2A in spermatogonia and spermatocytes, suggesting altered spermatogenesis. Additionally, an increased abundance of several extracellular proteins and small leucine rich repeat proteoglycans was observed, which may be related to impaired cell migration and fibrotic events. An increased abundance of proteins with inhibitory roles in smooth muscle cell contraction like CNN1, indicate functional alterations, specifically in peritubular cells and may mirror a reduced capacity of these cells, to contract in aged testes. In summary, these results document several age-associated changes in the testicular proteome of a non-human primate model and provides new insight into testicular aging.