Sideroxylon mascatense is a wild blueberry plant that traditionally known as “boot” in Oman. Studies on health beneficial effects of this fruit are very limited. Aims and Objectives: This study aimed to evaluate the antioxidant and antitumor properties of Sideroxylon mascatense under different drying methods. Materials and Methods: Freeze (−20°C) and air drying (60 and 90°C) methods were used. The antioxidant potential properties were evaluated using DPPH and ABTS assay. Moreover, the antitumor activities of blueberry extracts were determined using Alamar blue assay. Results: The results of this study revealed that a blueberry extract at 20 mg powder/mL provided the maximum amount of vitamin C, reaching a value of 19.45 mg/100 g dry-basis in the flesh dried at 60°C and 14.24 mg/100 g drybasis in seed dried at 90°C. The freeze-dried blueberry exhibited the highest percentage of free radical scavenging activity (DPPH) from both fruit flesh (50.8%) and seeds (39.4%) at a concentration of 20 mg/mL indicating a higher antioxidant activity. There was no significant difference in the ability of blueberry extracts to scavenge radical cations (ABTS+ ) at various concentrations of extracts. However, there was a 40% reduction of ABTS+ radical formation in blueberry flesh extracts obtained from freeze-dried berry at a concentration of 20 mg/mL. On the other hand, blueberry seeds showed variation in the scavenging activity of the ABTS+ radical of 38% after different processing methods. 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 69mg/mL, respectively. Conclusion: Our findings indicated a potent antioxidant activity of Sideroxylon mascatense, but further research is required to isolate the active compounds in the fruit and test their effects in an experimental animal model.