Introduction: Root-knot nematodes are one of the most important groups of plant parasitic nematodes in terms of economic damage to agricultural products. Biological control is one of the most environmentally friendly methods for management of nematodes. Material and Methods: The effects of aqueous extracts of jimsonweed  (Datura stramonium), metel (Datura metel) and henbane (Hyoscyamus niger) was evaluated against Meloidogyne javanica on cucumber, under greenhouse condition, in this study. Cucumber plants were inoculated with suspension of eggs and second stage juveniles of nematode. After a week, 1.66% concentration of each plant extract were irrigated in the pots. Plants were harvested after 45 days and some plant growth parameters and nematode reproductive parameters were recorded. Results: The extract of any of the plants did not affect the number of knots on the roots and per gram of the roots. However, number of egg- masses per root and gram of root, treatments including nematodes and extracts had fewer masses compared to treatments without plant extracts. Final population and reproductive factor had also lower values in treatments with plant extract compared to treatments without it. In addition, the plant extracts had no negative effect on the growth factors of the cucumber in the greenhouse. Conclusion: The extracts of Datura stramonium, Datura metel and Hyoscyamus niger reduced the reproduction of nematodes respectively, therefore they can be considered as potential agents in biological control of root-knot nematodes.