Abstract Objective The aim of the present study was to assess the effect of probiotics/synbiotics supplementation on anthropometric measures in adults with diabetes, regardless of body weight. Methods PubMed, Scopus, Web of Sciences and the Cochrane Library were searched for randomized controlled trials (RCTs) up to February 10, 2021. The effect sizes were pooled with the use of an inverse-variance random-effects model. The methodological quality of studies as well as quality of evidence was assessed using standard tools. Results Twenty-seven RCTs met the inclusion criteria. Overall, compared with their respective control groups, probiotics/synbiotics supplementation resulted in a significant reduction in body weight (weighted mean difference [WMD]: -0.62 kg; 95% CI: -0.97, -0.28; I2 = 81.1%, n = 23 studies]), body mass index (WMD: -0.20 kg/m2; 95% CI: -0.33, -0.07; I2 = 78.4%, n = 25 studies), and waist circumference (WMD: -0.93 cm; 95% CI: -1.34, -0.53; I2 = 0%, n = 8 studies). However, no significant improvement was observed for hip circumference and waist to hip ratio. Conclusions Our analysis revealed that probiotics/synbiotics supplementation may assist with weight management in patients with diabetes, especially when used at higher doses, in younger adults, and in participants with obesity. However, more studies are needed to elucidate the anti-obesity effects of specific probiotic/synbiotic strains.