The technique of induced systemic resistance (ISR) is one of the most novel and durable approaches for managing plant parasitic nematodes. The current trial was conducted to study the efficacy of ascorbic acid and β-aminobutyric acid (BABA) against the root-knot nematode, Meloidogyne incognita under in vitro and in vivo conditions on tomato plants. The obtained results elucidated that ascorbic acid (LC₅₀ = 3426.76 and 965.66 mg l^-1) was more effective or toxic than BABA (LC₅₀ = 16028 and 8405.68 mg l^-1) towards the juveniles' mortality of the root-knot nematode (M. incognita) after 24 and 48 hrs of exposure, respectively. However, the estimated LT₅₀ values of ascorbic acid were in the range of 193.02 to 17.95 hrs, while BABA recorded LT₅₀ values in the range of 159.04 to 33.61 hrs. On the other hand, application of ascorbic acid suppressed tomato root galls, egg masses, and soil populations at 88.46, 91.79, and 43.67%, while BABA recorded 87.18, 73.40 and 49.52%, respectively. Some of the applied treatments relatively improved tomato growth indices. The effect of BABA and ascorbic acid was also evaluated as inducers on tomato plants against M. incognita. The results elucidated that BABA and ascorbic acid (at two rates) increased the total soluble phenol (TSN), total soluble protein (TSP), polyphenol oxidase (PPO) and peroxidase (POD), significantly.