Diabetes mellitus (DM) is a complex metabolic disease characterized by hyperglycaemia resulted from defects in insulin secretion or action, or both. Various studies have reported on the bidirectional relationship between DM and periodontal disease. A systematic search of the literature was performed in several databases, EBSCO Medline Complete, PubMed, Science Direct and a manual search for articles from 2000 until 2019. Literature that fulfilled the inclusion criteria were identified, and data measuring plaque index (PI), gingival index (GI), clinical attachment loss (CAL) and periodontal probing depth (PPD) were extracted and subjected to Random-effects meta-analysis. From 947 titles and abstracts screened, 11 articles were included for meta-analysis. It was found that PI, GI, CAL and PPD were significantly higher in DM children than in non-DM children according to the Standardized Mean different (SMD) and 95% confidence intervals (CI) (SMD 0.54, 95% CI 0.20-0.87, P = 0.002; SMD 0.63, 95% CI 0.39-0.87, P