Abstract: Background and Objective: Root-knot (Meloidogyne species) nematodes are one of the most important causes of reduced tomato (Solanum lycopersicum) yield in Iran. During a survey of a tomato field, M. incognita was identified from the rhizosphere soil samples. Materials and Methods: Fresh leaf extracts of neem (Azadirachta indica) and wild thyme (Thymus vulgaris), including positive control (fenamiphos 60 ppm), were investigated in vitro and in vivo for efficacy against M. incognita motility and reproduction. Results: In vitro, all treatments caused (p<0.05) mortality of second-stage juveniles (J2), with the highest mortality occurring under neem leaf extracts at 48 and 72 hrs exposure. In vivo, with tomato inoculated at 5000 J2/seedling, all treatments reduced (p<0.05) root galling, gall index, reproductive factor (Pi/Pf) and J2 in soil. Conclusion: Overall, following fenamiphos, plant extracts of neem had the highest efficacy in suppressing nematode population densities. Consequently, the neem leaf extract could be investigated as an alternative product to synthetic chemical nematicides on tomatoes under field conditions.