Strawberries are considered as one of the most important crops grown in Iran for fresh local consumption and export. Using plant growth regulators to improve yield parameters is suggested. In this research influence of arginine at different levels and application time on qualitative and quantitative characteristics of strawberry ‘Paros’ were considered. Strawberry plants were foliar sprayed with arginine at concentration of 0, 250 and 500 μM in two stages (30 days aft er planting and at the start of bloom) with a factorial experiment in a completely randomized design with four replications in greenhouse conditions. Results showed that fruits of treated plants by arginine at concentrations of 250 and 500 μM had improved qualitative and quantitative characteristics compared to control treatment. Different levels of arginine application increased yield, weight of primary and secondary fruits and number of their achenes (quantitative characteristics), total soluble solid, inducing sugar, titratable acidity, anthocyanin, phenol, and vitamin C (qualitative characteristics). Th e best result was obtained by the arginine application at the rate of 500 μM at 30 days after planting.