Although high-intensity interval training (HIIT) is an efficient method to improve vascular function, maximal oxygen consumption, and muscle mitochondrial capacity, acute HIIT overstresses the oxidative and immune systems and causes muscle soreness and damage. The aim of the present study was to investigate the effects of date seeds on exercise-induced oxidative stress and aerobic and anaerobic performance following HIIT sessions. Thirty-six physically active men and women aged 18-35 years were assigned to take 26g/d of date seed powder (DSP, n=18) or wheat bran powder (placebo, n=18) before and after HIIT workouts for 14 days. Total antioxidant capacity (TAC), oxidative stress index (OSI), total oxidant status (TOS), superoxide dismutase (SOD), glutathione peroxidase (GPx), uric acid, malondialdehyde (MDA), and 8-iso-prostaglandin F2α (8-iso-PGF2) were determined at baseline, at the end of the intervention, and 24 hours’ post-intervention. We used the Cooper and running-based anaerobic sprint test (RAST) to assess aerobic and anaerobic performance at the study’s beginning and end. Independent Student’s t tests, analysis of covariance, and repeated-measures analysis of variance (ANOVA) were used to compare the quantitative variables. Positive changes were observed in TAC, TOS, OSI, GPx, MDA, and VAS after intervention and at 24 h post-exercise (p<0.05). Likewise, peak power and fatigue index were significantly improved in DSP in comparison to the placebo group. Levels of SOD, uric acid, 8-iso-PGF2, VO2 max, and average power were not changed after training. Our results showed that date seed supplementation in active participants performing HIIT bouts ameliorated oxidative stress and improved performance parameters.