The relation of early menarche with type 2 diabetes mellitus (T2DM) remains inconsistent across studies. The objective of this systematic review and meta-analysis of published population-based observational studies was to assess the association between age at menarche and T2DM risk. We searched online data bases through December 2013 and examined the reference lists of pertinent articles. Summary relative risks (RRs) with 95 % confidence intervals (CIs) were calculated with a random-effects model. A total of 14 effect estimates from 10 eligible studies (three cross-sectional and seven cohort studies) included 315,428 participants and 22,085 cases of T2DM. Compared with the highest or middle category, women in the lowest category of age at menarche had higher risk of T2DM [summary RR (95 % CI) 1.22 (1.17, 1.28)]. These results were consistent between studies that conducted in the United States and in Europe. The association between age at menarche and T2DM was slightly stronger for cohort than for cross-sectional studies. These findings strongly support an association between younger age at menarche and increased risk of T2DM. Age at menarche may help identify women with increased risk of developing T2DM.