This study demonstrates that GroBiotic (R)-A, a commercially available prebiotic made from partially autolyzed brewer's yeast, can significantly enhance the biomass, protein content, and antioxidant activity of Spirulina platensis, which already possesses a rich nutrient profile. The findings demonstrate that these improvements could further increase the productivity of S. platensis used in aquaculture, food production, and health product manufacturing. The effects of GroBiotic (R)-A were evaluated by adding it to Zarrouk medium at various concentrations. Positive results were observed for biomass at all concentrations, except at 1 g/l, while the maximum protein level (70.88%) was found in the group supplemented with 0.25 g/l GroBiotic (R)-A. The antioxidant capacity was evaluated through the DPPH radical scavenging method, with positive effects observed at all doses. The most effective dosage was 0.25 g/l, showing a value of IC50 at 59.71 mu g/ml. The results demonstrate that GroBiotic (R)-A can enhance the biomass, protein content, and antioxidant activity in S. platensis cultures, and these benefits can be maximized by optimizing the dosage. Furthermore, this study is the first to investigate the potential of GroBiotic (R)-A to improve the nutritional qualities of Spirulina, highlighting its promising role in algae cultivation for enhanced food and health benefits.