The aim of this research was to study the effect of MnxOynanoparticles stabilized with L-methionine on the morphofunctional characteristics of the barley (Hordeum vulgareL.) crop. MnxOynanoparticles stabilized with L-methionine were synthesized using potassium permanganate and L-methionine. We established that MnxOynanoparticles have a diameter of 15 to 30 nm. According to quantum chemical modeling and IR spectroscopy, it is shown that the interaction of MnxOynanoparticles with L-methionine occurs through the amino group. It is found that MnxOynanoparticles stabilized with L-methionine have positive effects on the roots and seedling length, as well as the seed germination energy. The effect of MnxOynanoparticles onHordeum vulgareL. seeds is nonlinear. At a concentration of 0.05 mg/mL, there was a statistically significant increase in the length of seedlings by 68% compared to the control group. We found that the root lengths of samples treated with MnxOynanoparticle sols with a concentration of 0.05 mg/mL were 62.8%, 32.7%, and 158.9% higher compared to samples treated with L-methionine, KMnO4, and the control sample, respectively. We have shown that at a concentration of 0.05 mg/mL, the germination energy of seeds increases by 50.0% compared to the control sample, by 10.0% compared to the samples treated with L-methionine, and by 13.8% compared to the samples treated with KMnO4.