Sideroxylon mascatense is a wild blueberry plant that traditionally called boot in Oman. There is a lack of research on the influence of different processing methods and long-term storage on nutritional quality of blueberry. Therefore, the aims of this study were to determine the physico-chemical characteristics of Sideroxylon mascatense and evaluate the stability of phytochemicals (i.e. polyphenols and flavonoids) during different drying methods and their health functionality (i.e. antitumor activity). Freeze (-20 °C) and air drying (60 and 90 °C) methods were used. The chemical compositions were analyzed according to AOAC methods. The TPC and TFC analyzed using Folin-Ciocalteu reagent and Aluminum chloride colorimetric methods respectively. The stability of phenolic compounds was investigated at different storage temperatures: 90, 70, 60, 40, 20 and -20 °C. The antioxidant potential properties of the blueberries were also evaluated using DPPH and ABTS assay. Moreover, the antitumor activities of blueberry extracts were determined using Alamar blue assay. The moisture content of fresh blueberry flesh and seed were 64.5 and 32.9 g/100 g sample (wet basis). The crude protein and fat were higher in the seeds as compared to fresh flesh. The protein content in all dried samples was higher than the fresh samples. There was a significant decrease of fat from fresh to dried samples with higher loss of lipid at 90 °C. The total estimated carbohydrate in flesh sample was comparable to the freeze-dried samples. Glucose and fructose are the main sugars in boot with higher concentration in air drying at 60 °C. The low pH (i.e. 4.43) indicated that the blueberry can be considered acidic. Blueberry showed good content of phenolic compounds. There was a significant difference of total polyphenol content (TPC) and total flavonoid content (TFC) (P<0.05) in samples processed by different drying methods. At 90 °C, the TPC reached the maximum of 2.638 and 0.632 mg GAE/g DS in flesh and seed respectively. In contrast, the freeze drying method retains high TFC as compared to air drying method that caused a significant loss of TFC at 90 °C. The degradation of TFC in freeze dried samples at different storage temperatures: 90, 70, 60, 40, 20 and -20 °C exhibited same trend in which there was an increasing phase (i.e. dominating release of TPC) with a peak followed by a decreasing phase (i.e. marginal release of TPC and mainly decay of TPC). However, the storage of freeze dried wild blueberry at -20 °C as well as 20 °C may be important because they could maintain the stability of the phenolic compounds longer up to 90 days. This may help food industry for production of juice, jam and jelly and dried berry. Blueberry showed antioxidant potential properties. The freeze dried blueberry exhibited the highest % DPPH free radical scavenging activity from both flesh (50.76%) and seed (39.37%) at concentration of 20 mg/ml indicating a higher antioxidant activity. However, there was no significant difference at various concentrations of blueberry extracts on their ability to scavenge the radical cation (ABT$+). Blueberry showed also antitumor activity. Breast MCF7 and ovarian Ov2008 tumor cell lines were the most sensitive to the dried blueberry. The 50% growth inhibition (IC50) of the freeze dried blueberry extract at both cell lines was 64 and 69 ug/ml respectively. However, further extensive research is required to extract active compounds in blueberry and test their effects in mouse model (in vivo).