Background: Micronutrient interventions for Adult Attention-Deficit/Hyperactivity (ADHD) could be helpful. We used a naturally processed whole wheat grains supplement containing higher doses of micronutrients named Nutrition Bio Shield (NBS). We aimed to determine its effects on ADHD symptoms in adults. Methods: Fifty-two medication-free adults with ADHD were randomly assigned to receive 5 g of NBS supplement or placebo daily for eight weeks. Results: Twenty-three participants in the NBS group and 24 participants in the placebo group completed the study. After 8 weeks, compared with the placebo, the ADHD scores significantly decreased (mean difference 95%CI):-4. 9 (-8. 6 to-1. 1),p=0. 01,Cohen’s d=0. 74), and quality of life significantly improved (mean difference 95%CI): 5. 6 (0. 12 to 11. 3),p=0. 04,Cohen’s d=0. 59) in the NBS group. The observed side effects were minimal and did not differ statistically between groups. Conclusion: Quality of life increased during consumption of the NBS supplement, compared to the placebo. However, despite the statistically significant findings, these changes in ADHD symptoms were small and the clinical significance may be low (about 5%).