Abstract: The presence of Amaranthus spp. Plants showing symptoms caused by root-knot nematode infection were detected in soybean fields from the municipality of Palmitas, Soriano, and Colonia del Sacramento, Colonia - Uruguay. After weed plants collection with root knot nematodes, the causal agents were identified as Meloidogyne incognita and Meloidogyne javanica from their morphology, esterase phenotypes, and species-specific characterized sequence amplified region (SCAR) sequences. The modified version of Koch's postulates was used to confirm the pathogenicity of Meloydogine ssp. In Amaranthus species. Host capacity of Amaranthus species for root-knot nematodes aggravates the harmful potential of the presence of these plants in crop fields. Therefore, control of these weed species, which allow for the reproduction of these parasites, might be an important tool for its management. This is the first report of root-knot nematodes M. incognita parasitizing A. hybridus and A. tuberculatus; and M. javanica parasitizing A. palmeri, A. hybridus and A. tuberculatus in Uruguay.