BACKGROUND & AIMS Gastrointestinal symptoms are among the most frequent reported complaints by people living with HIV and AIDS (PLWHA). Treatments that aim to attenuate these symptoms are important to avoid low adherence to antiretroviral therapy and to improve the quality of life. This study aimed to evaluate the effectiveness of nutritional treatment and synbiotic use in PLWHA on reducing gastrointestinal symptoms. METHODS A randomized clinical trial nested to an outpatient cohort was conducted to evaluate the effectiveness of two treatments for gastrointestinal symptoms reduction in adult patients with antiretroviral therapy presenting at least one gastrointestinal symptom: 1) nutritional treatment + placebo (6 g maltodextrin) and 2) nutritional treatment + synbiotic (Lactobacillus and Bifidobacterium strains + 6 g fructooligosaccharides). Placebo and synbiotic were consumed twice a day during six months. The primary outcome variable was percentage reduction in the incidence of diarrhea, and secondary outcomes the decrease in the incidence of nausea and/or vomiting, dyspepsia, heartburn, constipation, flatulence, and the presence of three or more gastrointestinal symptoms. RESULTS Out of 283 patients evaluated for eligibility, 64 met inclusion criteria to enter in this study with 1:1 allocation ratio. Both analyzed groups were homogeneous regarding sociodemographic, clinical and lifestyle variables at baseline. In the intergroup analysis, no difference was found between groups except for heartburn, which had a higher reduction in the placebo group (0.01). Regarding the intragroup analysis, in the placebo group a significant decrease in diarrhea (p = 0.02) and heartburn (p < 0.01) were observed while there was a significant reduction for nausea e/or vomit (p = 0.01), dyspepsia (p = 0.10), diarrhea (p = 0.01) and constipation (p = 0.08) in the synbiotic group. CONCLUSIONS Diarrhea decreased in both groups, but no statistical difference between treatments was observed. The use of synbiotic appeared to reduce a greater number of symptoms although there were no statistical differences in the intergroup analysis. This clinical trial was registered at ClinicalTrials.gov (NCT02180035).