The rachis browning phenomenon is an urgent problem in the grape trade where it is not acceptable to customers. The research was conducted in two successive growing seasons (2020-2021) to assess the influence of calcium nanoparticles (CaNPs) coupled with oxalic acid (OXA) in various concentrations on decreasing the browning phenomenon of rachis and maintaining the quality of 'Superior Seedless' grape bunches during shelf-life period. Bunche samples were taken from a private vineyard when SSC was about 16%. The grapes were stored for three days at laboratory temperature (at 27 ± 1 ° C and 46 ± 2% relative humidity). Result showed that the CaNPs-20 mM OXA significantly maintained the freshness of clusters rachis by reducing the rate of water loss, repressing the development of brown pigments and preserving the hue angle of rachis. Also, it maintained the soluble solids content and SSC:TA-ration, while it delayed the decreases of total acidity and ascorbic acid content, which showed the better maintenance of chemical content in the treated bunches. Besides, a notable decrease in the enzyme activities of cell walls such as polygalacturonase, xylanase, cellulase, and pectinase was observed. Also, the contents of total phenol and flavonoid have increased, while polyphenol oxidase and phenylalanine ammonia-lyase have decreased. Also, the CaNPs-20mM OXA reduced malondialdehyde accumulation, lipoxygenase activity and the rachis electrolyte leakage percentage throughout the shelf-life duration. summary, CaNPs-20 mM OXA proved to be an effective treatment for maintaining the quality of 'Superior Seedless' bunches during the shelf-life duration.