In the intestinal flora, there seems to be about 500 microorganism species and 98% of them are found to be useful. However intestinal flora can contain different microorganisms in each individual. Probiotics and prebiotics might have beneficial effects such as increasing immunity, preventing inflammation by stimulating inflammation-inhibiting cytokines, inhibiting the reproduction of pathogens and the involvement of viruses. Irritable Bowel Syndrome (IBS) and Functional Dyspepsia (FD) are disorders associated with upper gastrointestinal system symptoms in addition to symptoms such as abdominal pain, diarrhea and / or constipation, bloating, early satiety, and nausea. Abdominal pain, gas, bloating and nausea complaints are common and very difficult to treat in IBS and FD patients, and may affect the social life and quality of life of the individual. Probiotics and prebiotics are claimed to be effective in treating these symptoms with positive effects on the health of the individual. This review evaluates and summarizes the literature on the use of probiotics and prebiotics as a treatment and their efficacy in reducing the symptoms in IBS and FD patients.