WHAT IS KNOWN AND OBJECTIVE: Aloe vera (Aloe vera (L.) Burm.f., Xanthorrhoeaceae family) has long been used in folk or traditional medicine for diabetes. Several studies have been conducted on the effect of Aloe vera on glycaemic control, but the results appear inconsistent. We undertook a systematic review and meta-analysis to assess the effect of Aloe vera on glycaemic control in prediabetes and type 2 diabetes. METHODS: A comprehensive literature search was conducted through MEDLINE, CENTRAL, CINAHL, Scopus, http://clinicaltrials.gov, Web of Science, Proquest, LILACS, HerbMed, NAPRALERT and CNKI to the end of January 2016 without language restriction. Historical search of relevant articles and personal contact with experts in the area were also undertaken. Studies were included if they were (1) randomized controlled trials of Aloe vera aimed at assessing glycaemic control in prediabetes or type 2 diabetes and (2) reporting fasting plasma glucose (FPG) or haemoglobin A1c (HbA1c ). Treatment effect was estimated with mean difference in the final value of FPG and HbA1c between the treatment and the control groups. RESULTS AND DISCUSSION: Eight trials involving 470 patients (235 each for prediabetes and type 2 diabetes) were included. In prediabetes, Aloe vera significantly improved FPG (mean difference -0·22 mmol/L, 95% CI -0·32 mmol/L to -0·12 mmol/L, P < 0·0001), with no effect on HbA1c (mean difference -2 mmol/mol, 95% CI -5 mmol/mol to 1 mmol/mol). Aloe vera may improve glycaemic control in type 2 diabetes, with a marginal improvement in FPG (mean differences -1·17 mmol/L, 95% CI -2·35 mmol/L to 0·00 mmol/L, P = 0·05) and a significant improvement in HbA1c (mean difference -11 mmol/mol, 95% CI -19 mmol/mol to -2 mmol/mol, P = 0·01). WHAT IS NEW AND CONCLUSIONS: The current evidence suggests some potential benefit of Aloe vera in improving glycaemic control in prediabetes and type 2 diabetes. However, given the limitations of the available evidence and the high heterogeneity in study results, high-quality, well-powered randomized controlled trials using standardized preparations are needed to quantify any beneficial effects of Aloe vera on glycaemic control.