Background <p>Given the rising prevalence of gestational diabetes and its substantial impact on both fetal/neonatal outcomes and maternal postpartum health, understanding factors that influence effective management of the condition is of paramount importance.</p> Methods <p>This multicentre cross-sectional study was conducted between February and November 2023 on 319 women with gestational diabetes mellitus at three tertiary hospitals in Fujian, China. The participants completed self-report questionnaires on their demographic characteristics, personality traits, self-efficacy, self-management, and social support. A structural equation model identified associations among personality traits, self-efficacy, and self-management.</p> Results <p>Among the 303 (94.98%) women included, education level, household income, abortion history, and prematurity history were associated with self-efficacy, while education level and household income were linked to self-management. Conscientiousness and extraversion positively influenced self-efficacy (<i>β</i> = 0.291, 0.378, <i>P</i> = 0.001), with conscientiousness also affecting self-management (<i>β</i> = 0.285, <i>P</i> &lt; 0.05). Social support mediated the relationships between personality traits, self-efficacy, and self-management.</p> Conclusion <p>Efforts to improve self-efficacy and self-management behaviours in women with gestational diabetes may benefit from focusing on personal traits and increasing social support.</p>