Application of natural and safety compounds is an effective method to maintain the quality and improve the marketability of stored strawberries. In this research, the effect of trans-cinnamic acid in delaying the senescence, maintaining the quality, and improving the marketability of strawberry fruit cv. Monterey at the end of the storage (10 days at 1±1°C and 24 hours at room temperature) was investigated. The postharvest treatment of trans-cinnamic acid in concentrations of 0.1, 0.2 and 0.3 g/L reduced ion leakage, malondialdehyde and other aldehydes contents as the indicators related to strawberry fruit senescence. Also, trans-cinnamic acid treatment increased total anthocyanin content of strawberry fruits approximately 12.5 %, 19 % and 14.5 % and total antioxidant activity of berries 6.8 %, 10.7 % and 9.2 % respectively compared to control one. These results showed a negative and significant correlation with senescence related parameters. Strawberries treated with trans-cinnamic acid had better color and taste compared to the control. Statistically, trans-cinnamic acid did not show a significant effect on the firmness of strawberry fruits. Also, trans-cinnamic acid in different concentrations improved the marketability of strawberry fruit 13 %, 20 % and 9 % respectively, compared to control one. In general, the results of this research indicated that the post-harvest application of trans-cinnamic acid, especially at the 0.2 g/L, has considerable effects on maintaining quality and improving marketability of stored strawberry fruits via delaying senescence and increasing the antioxidant activity of strawberry fruits.