Boron (B) nanofertilizers are an innovative alternative with great potential to make nutrient application more efficient and thereby improve crop growth and productivity. However, nowadays there is little literature on the effects of boron nanofertilizers on physiological and biochemical processes in plants. Therefore, the objective of the present research was to study the efficacy of foliar application of a boron nanofertilizer on biomass, yield, nitrogen assimilation and photosynthetic activity in green beans plants cv. Strike. The B nanofertilizer was foliar applied at 0, 25, 50 and 100 ppm. Biomass accumulation, yield, nitrate reductase enzyme activity, photosynthetic activity, stomatal conductance and photosynthetic pigment content were evaluated. The results obtained indicate that the application of B nanofertilizer at dose of 25 ppm were more effective in improving biomass, while the dose of 100 ppm favoured nitrate reductase activity and stomatal conductance. The results suggest that the application of B nanofertilizers stimulated the development of green bean plants. Finally, more studies are needed to evaluate the possible phytotoxic effects of high doses of B nanofertilizers and to compare their effects with conventional B fertilizers already used in the market.