Plant parasitic nematodes are dangerous pests for many crops including tomatoes. In this work, in vitro and in vivo nematocidal properties of the fungus Verticillium lecanii and hydrogen peroxide were compared to the commercial nematicide, melithorin® (90% fosthiazate), and assessed against the root-knot nematode Meloidogyne incognita. Results indicated that application of melithorin® (1 mL/L) recorded the highest nematode mortality of 89.4% after 96 hours of in vitro application, followed by hydrogen peroxide (150 mM) and Verticillium lecanii (100%) recording 33.7% and 22.1% mortality, respectively, after the same time of application. In the greenhouse trial, melithorin® recorded the highest reduction in nematode galls, egg masses, females, development stages, and 2nd juveniles by 86.15%, 93.89%, 67.81%, 73.22%, and 79.48%, respectively, followed by Verticillium lecanii recording 44.72%, 44.02%, 43.12%, 51.48%, and 34.54% and then hydrogen peroxide (29.96%, 27.98%, 22.5%, 37.75%, and 29.09%, resp.). Infection alleviation was investigated by measuring infected tomato plant growth parameters, photosynthetic pigments, antioxidant enzymes, total proteins, free proline, total phenols, malonaldehyde (MDA), and hydrogen peroxide (H2O2) contents. Results indicated that the application of melithorin® followed by hydrogen peroxide and then Verticillium lecanii showed significant improvements in tomato vegetative growth and biochemical markers. Therefore, it is possible to consider Verticillium lecanii and hydrogen peroxide to be cheap and efficient nematocidal treatments.