Objective: To assess the association between interpregnancy interval (IPI) and gestational diabetes mellitus (GDM). Methods: Data of this retrospective cohort study were obtained from the National Vital Statistics System (NVSS) 2020. The participants were divided into different groups according to different IPI (<6, 6–11, 12–17, 18–23, 24–59 (reference), 60–119, ≥120 months). Multivariate logistic models were constructed to evaluate the association between IPI and GDM. Subgroup analysis was further performed. Results: A total of 1 515 263 women were included, with 123 951 (8.18%) having GDM. Compared with the 24–59 months group, the <6 months (odds ratio [OR] 0.64, 95% confidence interval [CI] 0.46–0.90, P = 0.009), 12–17 months (OR 0.96, 95% CI 0.94–0.98, P < 0.001), and 18–23 months (OR 0.94, 95% CI 0.93–0.96, P < 0.001) groups had a significantly lower risk of GDM, while the 60–119 months (OR 1.13, 95% CI 1.11–1.15, P < 0.001) and ≥120 months (OR 1.18, 95% CI 1.15–1.21, P < 0.001) groups had a significantly higher risk of GDM. No significant difference was observed in the risk of GDM between the 6–11 and 24–59 months groups (P = 0.542). The PI–GDM association varied across different groups of age, pre‐pregnancy body mass index, pre‐pregnancy smoking status, history of cesarean section, history of preterm birth, prior terminations, and parity. Conclusion: An IPI of 18–23 months may be a better interval than 24–59 months in managing the risk of GDM. Synopsis: A period of 18–23 months may be a better interpregnancy interval than 24–59 months in managing the risk of gestational diabetes mellitus. [ABSTRACT FROM AUTHOR]