BackgroundDespite that several original researchers have investigated the association between neck circumference (NC) and the risk of diabetes mellitus (DM), their results remain controversial. This review aimed to quantitatively determine the risk of DM in relation to the NC.MethodsWe conducted a literature search of PubMed, Embase, and the Web of Science from these databases’ inception through September 2022 to identify observational studies that examined the association between NC and the risk of DM. A meta-analysis of the random-effects model was applied to combine the results of the enrolled studies.ResultsSixteen observational studies involving 4,764 patients with DM and 26,159 participants were assessed. The pooled results revealed that NC was significantly associated with the risk of type 2 DM (T2DM) (OR = 2.17; 95% CI: 1.30–3.62) and gestational DM (GDM) (OR = 1.31; 95% CI: 1.17–1.48). Subgroup analysis revealed that after controlling for BMI, the relationship between the NC and T2DM remained statistically significant (OR = 1.94; 95% CI: 1.35–2.79). Moreover, the pooled OR of T2DM was found to be 1.16 (95% CI: 1.07–1.27) for an increment per each centimeter in the NC.ConclusionsIntegrated epidemiological evidence supports the hypothesis that a greater NC is associated with an increased risk of T2DM and GDM.Supplementary InformationThe online version contains supplementary material available at 10.1186/s13098-023-01111-z.