Introduction: Cherry is one of the most popular and important horticultural products for the food processing industry. Since polyamines compounds in postharvest processing have a special role, this study was conducted to examine the effect of polyamines on the firmness and the shelf life of cherries after harvesting.Materials and Methods: In this study, 16 trees of 19 years old with the same growth condition were randomly selected. After selecting the healthy branches the external parts were treated with two types of polyamines, spermidine and putrescine in triplicate orders. The former was applied at the concentrations of 0.1, 0.5 and 1 mM and the latter at 0.5 and 1 mM. External applications of polyamines were carried out in three phenological stages, 5 to 10 days before the full bloom, 5 to 10 days after the full bloom and the staining.Results: After treatment, characteristics such as fruit size, fruit weight, acidity (TA), soluble solids, percent carbohydrate, and ratio of soluble solids to acidity were measured. Spermidine 1 mM treatment increased size and weight, and also increased the amount of carbohydrates and fruit firmness.Conclusions: Treatment of polyamines, especially spermidine in 1 mM increased the firmness and durability and the effect strongly depends on the time of spraying and the concentration of these compounds.