This comprehensive review examines how baker’s yeast (Saccharomyces cerevisiae) is being used as a probiotic supplement in fish farming and aquaculture. The research shows that adding this yeast to fish feed improves growth rates, helps fish fight off diseases, and creates healthier gut bacteria in aquatic animals. Scientists worldwide are increasingly studying this natural alternative to antibiotics, with studies demonstrating benefits across various fish species including tilapia, trout, and catfish, making it an important tool for sustainable and healthier aquaculture practices.