In this work, we are reporting, for the first time, a parasitoid wasp associated to the nests of Mischocyttarus cerberus, also we provide information concerning the parasitoid behavior when close to its host. We believe that the parasitism process is not easily accomplished, because the host resident females keep guarding and attacking whenever they detect any kind of parasitoid approach. Our results provide more detailed and important information about the host-parasitoid interaction behavior involving the Pachysomoides sp. and M. cerberus, which so far is scarce scientific literature.