Sarinda marcosi Piza, 1937 is an ant-like jumping spider that shares its microhabitat with the carpenter ant Camponotus mus Roger, 1863 (Hymenoptera: Formicidae). The objectives of this study were to record S. marcosi from Uruguay, to describe the type of mimicry present in this species, and to determine the ant model it mimics and how closely it resembles it. We recorded measurements of the prosoma, opisthosoma and sternum of S. marcosi and Aphirape flexa Galiano, 1981 (Salticidae), a sympatric non-mimetic jumping spider, to calculate mimicry indices as indicators of mimicry. We created three experimental groups in which we exposed: (1) S. marcosi vs. C. mus, to test Peckhamian mimicry; (2) S. marcosi vs. A. flexa, to test the response of S. marcosi in front of a potential predator; and (3) A. flexa vs. one juvenile of Phiale roburifoliata Holmberg, 1875 (Salticidae), to test the response of A. flexa in front of a non-mimetic jumping spider (n = 15, for each experimental group). We observed similarities between S. marcosi and C. mus, both in coloration and morphology. All mimicry indices obtained were indicators of mimicry for S. marcosi. There were no attacks by S. marcosi towards C. mus and no successful attacks of A. flexa on S. marcosi, but A. flexa successfully attacked P. roburifoliata. According to these results, S. marcosi is a Batesian mimic and C. mus serves as its model. This study indicates that mimicry provides protection against predators to S. marcosi. Additionally, we provided new data about the taxonomy of the spider.