The prevalence of type-2 diabetes mellitus (T2D) is increasing worldwide and there are no long-term preventive strategies to stop this growth. Emerging research shows that perturbations in the gut microbiome significantly contribute to the development of T2D, while microbiome modulators may be beneficial for T2D prevention. However, microbiome modulators that are effective, safe, affordable, and able to be integrated daily in the diet are not yet available. Based on our previous pro- and prebiotic studies, we developed a novel synbiotic yogurt comprised of human-origin probiotics and plant-based prebiotics and investigated its impact on diet- and streptozotocin-induced T2D in mice. We compared the effects of our synbiotic yogurt to those of a commercially-available yogurt (control yogurt). Interestingly, we found that feeding of this synbiotic yogurt significantly reduced the development of hyperglycemia (diabetes) in response to high-fat diet feeding and streptozotocin compared to milk-fed controls. Surprisingly, the control yogurt exacerbated diabetes progression. Synbiotic yogurt beneficially modulated the composition of gut microbiota compared to milk; conversely, the control yogurt negatively modulated the gut microbiota by significantly increasing the abundance of detrimental bacteria like Proteobacteria and Enterobacteriaceae. In addition, the synbiotic yogurt protected intact pancreatic islet morphology compared to the milk control, while the commercial yogurt demonstrated worse effects on pancreatic physiology. These results suggest that our newly developed synbiotic yogurt protects against diabetes in mice and can be used as a modality to prevent diabetes progression.