Introduction: Probiotic yoghurt is considered a functional food and has beneficial effects on human health. In some animal studies, the effects of probiotics in decreasing plasma glucose and delaying the onset of hyperglycemia and insulin resistance have been reported. Considering the ever-increasing prevalence of type 2 diabetes, the aim of the present study was to investigate the effects of probiotic yoghurt on diabetes markers and insulin resistance in type 2 diabetic patients. Materials and Methods: This double-blind, randomized clinical trial was conducted on 60 type 2 diabetic patients that had referred to endocrine and metabolism clinic of Sina hospital in Tabriz. Subjects in the intervention group consumed 300 grams of probiotic yoghurt daily, while those in the control group consumed 300 grams of conventional yoghurt daily for 6 weeks. Dietary intakes, anthropometric measurements, fasting blood sugar, insulin, glycosylated hemoglobin and insulin resistance were measured at baseline and at the end of the study. Paired Samples t-test and Analysis of Covariance were performed by SPSS software for statistical analyses. Results: Mean fasting blood sugar and glycosylated hemoglobin were significantly different between two groups after intervention (P<0.05). In the probiotic yoghurt consumption group, fasting blood sugar decreased significantly throughout the study (P<0.01), whereas, reductions in insulin concentration, glycosylated hemoglobin and insulin resistance in this group were not significant (P>0.05). Conclusion: Considering the positive effect of probiotic yoghurt in reducing fasting blood sugar in type 2 diabetic patients, consumption of probiotics is recommended as auxiliary therapy in these patients.