This experiment was carried out during the two successive winter seasons of 2018/2019 and 2019/2020 at El-Khattara Experimental Farm, Fac. Agric., Zagazig University, Sharkia Governorate, Egypt to study the effect of mineral nitrogen levels and foliar spray with tryptophan amino acid in different concentrations on the growth, yield and quality of lettuce plants cv. Dark green under sandy soil conditions. The best interaction treatment for increasing head weight, total yield and leaf area index was fertilizing plants with mineral nitrogen at 75% of recommended dose (RD) and spraying with tryptophan at 30 ppm. Moreover, fertilizing with 75% N (RD) and spraying with tryptophan at 45 ppm gave the highest values of total dry weight/ plant, N, K and dry matter percentage. In addition, fertilizing lettuce plants with 100% N (RD) and spraying with  tryptophan at 30 (ppm) increased P%, whereas the highest nitrate concentration in leaves recorded by the interaction treatment with 100% N (RD) and all tested concentrations of tryptophan. Therefore, fertilizing with 75 % N (RD) and spraying with tryptophan at 30 ppm could be recommended for raising lettuce yield and giving moderate value of nitrate concentration in leaves under conditions of this study.