With the purpose to find-out the effect of the herbicide Paraquat on the population of Collembola families. This study was carried-out in 2014 on a grassland ecosystem. In this study 2 treatment with the herbicide Paraquat were applied during a period of 6 months. Specimens were collected using pitfall traps and obtained a total of 6 418 specimens, distributed in 8 families, located in the area sampled. The area with the most abundance of specimens of Collembola, was those trealed with 2 applications of Paraquat during 6 months, sampled followed by monthly aplications and finally the area in which the herbicide was not applied. The areas treated with the herbicide showed more populations in 7 of 8 families found in the area, being Entomobyidae family the most abundant specimens, more than the 3 areas sampled, specially in the area treated with the herbicide.