Association between metabolic syndrome (MetS) and oxidative stress has been shown in numerous studies. It has been shown that probiotics could be the effective treatment strategy in improving oxidative stress. This study aimed to determine the effects of a new developed synbiotic yogurt on oxidative stress status in adults with MetS. Forty-four individuals were assigned into two groups and given 300 g of synbiotic yogurt containing Lactobacillus plantarum, Lactobacillus pentosus, and Chloromyces marcosianos yeast or regular yogurt for 12 weeks in this randomized, placebo-controlled clinical trial. Before and after the intervention, biochemical parameters were assessed. Daily consumption of synbiotic yogurt in adults with MetS showed a statistically significant improvement in the level of glutathione peroxidase (p = 0.01) and total oxidant status (p = 0.006) compared to the regular yogurt. Total Antioxidant Capacity and superoxide dismutase levels increased significantly (p = 0.002 and p = 0.02, respectively) in the intervention group compared to the baseline levels. In adults with MetS, daily consumption of the synbiotic yogurt containing native strains of Lactobacillus plantarum, Lactobacillus pentosus, and Chloromyces marcosianos yeast for 12 weeks was associated with improvements in oxidative stress status.Trial registration number: Iranian Registry of Clinical Trials (IRCT20220426054667N1) (18/05/2022).