Demand for organic products is growing; Amino acid is an organic form of nitrogen that can increase plant growth and yield, but no comprehensive research has been done on various vegetables. This experiment was performed to evaluate different levels of amino acids (zero, 3, 4 and 6 mg / l) in a completely randomized design with four replications in the greenhouse of Isfahan University of Technology on two important vegetables: tomatoes and bell peppers. The results showed that the amino acid at a concentration of 6 mg / l increases the fresh and dry weight of tomato shoots and fresh weight of bell pepper root. The dry weight of bell pepper fruit in treatment 4 and in tomato in 3 mg / l amino acid treatment increased significantly compared to the control treatment. Amino acid application did not have a significant effect on solids and fresh weight of fruit, but caused a significant increase in tomato fruit diameter. Amino acid application did not have a significant effect on the absorption of elements in bell peppers, but increased the absorption of potassium and phosphorus in tomatoes. In general, the test results showed an increase in growth and yield of the studied plants; However, more research is needed and more amino acid concentrations are needed on different vegetables.