Root-knot nematode, Meloidogyne javanica is a major causal agent of plant diseases on summer crops in fields and greenhouses. In order to reduce environmental concerns, compounds having pesticidal capacity with insignificant residue can be a good alternative to synthetic pesticides. This study was undertaken to investigate the nematicidal capability of ozone under Petri dish (in vitro) and pot (in the rhizosphere of tomato seedlings cv. Super Chief) conditions. The experiments were conducted based on Completely Randomized Design in four replicates with two antimicrobial materials, Cadusafos (0.5, 1.0, 1.5, 2.0, 2.5 and 3 g kg-1 soil) and ozone (0.05, 0.1, 0.2, 0.4, 0.8 and 1.6 g kg-1 soil). Results confirmed the significant in vitro controlling effect of ozone on nematode egg (85%, in 0.4 g kg-1 soil) and second stage juvenile (72%, in 0.4 g kg-1 soil) populations. Also a toxic effect of ozone was observed on the nematode pathogenicity, i.e. galling (83%, in 0.4 g kg-1 soil), on tomato root in pot assays. Plant morphological traits (i.e. root fresh weight, foliage fresh weight, and stem length) were not significantly affected by ozone. Therefore, taking into account the principles of safety in the application of ozone, this material can be suggested as an alternative nematicide, at least at limited and controlled condition.