Guavas are climacteric, perishable fruits and have very short life after harvest. Postharvest treatments of fruits by using oxalate or gibberellic acid and storage at low temperature can enhance storability of guava fruits without quality deterioration. This experiment was conducted in seasons (2015 and 2016) to evaluate the effect of potassium oxalate, ammonium oxalate and gibberellic acid (GA3) either alone or in combinations as postharvest treatments on physical and chemical changes of winter Guavas strain ‘Etmany' during storage at 8±1°C plus two days at 18-23°C as shelf life. Nine treatments were applied as follows: control (distilled water), 30 mM of potassium oxalate, 30 mM of ammonium oxalate, 50 or 100 ppm of GA3 and 30 mM of potassium oxalate or ammonium oxalate in combination with 50 or 100 ppm of GA3. The treated fruits were dipped in aqueous solution for 10 minutes. All treatments significantly reduced the deterioration in physical and chemical attributes compared to control treatment during cold storage and shelf life. Also, these treatments significantly minimized physiological loss in weight, reduced decay incidence, maximized marketable percentage, maintained visual appearance score, increased firmness, hue angle and lightness. Moreover, fruits treated with 30 mM of potassium or ammonium oxalate in combination with 100 ppm of GA3 possessed the best values in comparison with either control or the other treatments. Thus, it is been recommended from the results, to use the combination of potassium or ammonium oxalate and GA3 as a promising method for delaying postharvest deterioration and keeping fruit quality during cold storage up to 21 days at 8°C and 2 days shelf life at 18-23°C.