Background: Biostimulants are amino acids and organic components, which can play main role in the plant growth and dry matter accumulation.

Objective: Determine the influence of foliar application of active amino acids on quality and quantity yield of Melissa officinalis L.

Methods: This study was conducted in a research farm at the institute of medicinal plants on the base of randomized complete blocks design (RCBD) with three replications. The treatments were control (foliar application with distilled water) and commercial formulations of aminolforte, kadostim, fosnutren, and humiforte (each of them 2 L ha^-1), and chemical fertilizer (70 kg ha^-1 N.P.K).

Results: The results indicated that a significant increase in the content of citronellal, neral, delta-cadinene, germacrene, and geranial, were found in response to aminolforte and fosnutren application. The essential oil content was also increased through using kadostim and chemical fertilizer. A significant improvement in the plant height, number of flowers per stem, and SPAD value were observed in response to the foliar application of aminolforte. Morover, foliar application of fosnutren improved leaf length, leaf number, leaf area, leaf dry weight, and shoot dry weight, accordingly. There was no variation in the number of branches per plant among the treatments of kadostim and aminolforte both of these treatments improved the attribute.

Conclusion: The foliar application of free amino acids based on commercial formulations including aminolforte, kadostim, humiforte, and fosnutren can be effective on the quality and quantity yield of lemon balm.