To assess the effectiveness of foliage spray of nitric oxide (NO) on some key physio-biochemical variables of tomato (Lycopercison esculentum cv. ‘Target NF1’) plants subjected to boron (B) toxicity, a glasshouse trial was established. A factorial experiment was conducted with three levels of B (0.5, 3.5 and 6.5mg/L) and 0 or 0.1mM NO as foliar spray. Boron toxicity caused marked decrease in dry matter and fruit yield in tomato plants as compared to non-stresses plants, but increased electrolyte leakage (EL), proline, malondialdehyde (MDA) and hydrogen peroxide (H 2 O 2 ) contents coupled with superoxide dismutase (SOD; EC 1.15.1.1), peroxidase (POD; EC. 1.11.1.7), catalase (CAT; EC. 1.11.1.6) activities and total antioxidant activity (TAA). However, exogenous application of NO partly mitigated the damaging effects of B toxicity on key growth parameters which due to low membrane permeability, H 2 O 2 and MDA contents, TAA and antioxidant enzyme activities. Leaf B was higher in tomato plants at B treatments than that in the control plants. High B reduced leaf Ca 2+ , N and K + as compared to those in the control plants. Foliar application of NO lowered B concentration and increased Ca 2+ , K + and N levels in the leaves. The study clearly reveals that exogenous NO can overcome the deleterious effects of B toxicity on tomato fruit yield and whole plant biomass by reducing the concentrations of B, MDA and H 2 O 2 as well as electrolyte leakage in the leaves.