The aim of this study was to determine the effect of mustard (Sinapis alba L.) and marigold (Tagetes patula L.) plant - parasitic and other types of nematodes in red onion. The experiment was set in March 2016 in the village Strizivojna in three treatments (onion - mustard, onion - marigold and onion (control) and four repetitions. The largest number of nematodes in 100 g of soil was found in the treatment with onion - marigold (1249), whereas the lowest number was in the treatment only with onion (control) (419). Number of families ranged from 11 - 15. Nematode genera that was found in all treatment were: Rhabditis, Acrobeloides, Aphelenchus, Aphelenhoides and Eucephalobus. Bacterivorous and fungivorous nemaodes were the most dominant trophic groups, while the least represented were plant - parasites, predators and omnivores. Disturbance indicies showed that the treatment with onion (control) demonstrated the maximum value MI and MI (2-5), while minimum values were found in treatment with onion - mustard and onion - marigold. PPI index values ranged from 2.1 to 2.6., while the ratio of PPI / MI indicated disturbance in the soil. Statistically significant difference between treatments was found in the number of nematodes / 100 g of soil, percentage of bacterivoruous nematodes and predators, and MI and MI (2-5). The indexes of food chain statistically did not differ significantly between treatments. According to the results it is evident that the marigold showed the best impact on nematode community in the soil. .