Background To evaluate the efficacy of probiotics in the treatment of gingivitis. Methods MEDLINE, EMBASE and CENTRAL were searched up to May 2019. Randomized controlled clinical trials (RCTs) and/or controlled clinical trials were considered. Studies consisting of >= 10 patients per group clinically diagnosed with gingivitis were selected that compared the efficacy of probiotics in any form with placebo. The primary outcome measure was bleeding on probing (BOP) and gingival index (GI), while the secondary outcome measure was plaque index (PI). Forest plots were created reporting weighted mean difference (WMD) of outcomes with 95% confidence intervals (CI). Results A total of 10 double-blind placebo-parallel RCTs were included. All studies showed that probiotic administration was effective in the treatment of gingivitis at follow-up. The mean percentage of BOP ranged from 11.87% to 21.7% in the probiotics group and from 15% to 33% in the placebo groups at follow-up, respectively. Considering the effects of Lactobacillus reuteri, the overall mean difference for GI (WMD = -0.48, 95% CI = -1.69 to 0.72, P = 0.42) and PI (WMD = 0.18, 95% CI = -0.23 to 0.61, P = 0.37) did not show any statistical significance between probiotic and placebo groups. Conclusions The outcomes of this review show weak evidence to support the use of probiotics in reducing inflammatory periodontal parameters in gingivitis. Significant heterogeneity and limited available data may reduce the impact of these conclusions.