THE EFFECTIVENESS of postharvest treatments of sodium nitroprusside (SNP), oxalic acid (OA) and hydrogen peroxide (H₂O₂) treatments and their combinations on postharvest quality and enzyme activity of ‘Valencia' orange fruits were examined after harvest in season 2014 and 2015. The experiment were included the following treatments: distilled water (control), 1 mM SNP, 10 mM OA, 2% H₂O₂, 1 mM SNP + 10 mM OA, 1 mM SNP + 2% H₂O₂ and 10 mM OA + 2% H2O2 for 5 minutes. All treatments were stored at 8±1°C and 85-90% relative humidity (RH) followed by one week as a shelf life at ambient temperature 18-23°C and 55-65% RH for 15 weeks. All postharvst studied maintained postharvest quality of ‘Valencia' oranges as compared to untreated fruits (control) during storage. Moreover, combined treatments were more effective than individual treatments. Treated ‘Valencia' oranges with 1 mM SNP plus 10 mM OA or 2% H2O2 alleviated decay incidence and reduced weight loss percentage with an increase of marketable fruit percentage. In addition, these applications reduced the activities of polyphenol oxidase (PPO) and pectinase (PE) enzymes, while increased the activity of peroxidase (POX) enzyme. These treatments also decreased loss of firmness, hue angle, lightness values and juice content of fruits. In addition, these applications slowed the increase of soluble solids content (SSC) and SSC/TA ratio as well as decreased loss of titratable acidity (TA) and ascorbic acid contents during cold storage period followed by shelf life. Therefore, the use of postharvest treatments with 1 mM SNP in combination with 10 mM OA or 2% H2O2 have good potential strategy to improve the storability and reduce decay incidence as well as maintain postharvest quality of ‘Valencia' oranges during cold storage.