Guava is a tropical fruit with high nutritional value, but it is highly perishable. In this study, fruits treated with 1% and 2% oleic acid solely or in combination with cinnamon essential oil, then stored at 10±1 °C and 90-95% RH for four weeks, and the quantitative and qualitative characteristics of fruits were evaluated. The results showed that the treatments were more effective in maintaining the qualitative characteristics of the fruits as compared to the control. Treatments of 1% oleic acid and 1% cinnamon essential oil showed more significant effects by preventing weight loss, maintaining flesh firmness, and reducing chlorophyll and color change. Fruits treated with 1% oleic acid and 1% cinnamon essential oil showed the highest content of ascorbic acid, total phenol content, total flavonoid content and antioxidant activity and the lowest polyphenol oxidase activity during 28 days of storage. The highest total soluble solids (TSS), fruit flavor index (TSS/TA), and the lowest titratable acidity (TA) were obtained in control treatment. These results indicated that oleic acid treatment with cinnamon essential oil can be a useful method for delaying ripening and senescence, increasing storage life and preserving guava fruit quality.