Life expectancy for individuals with type 1 diabetes mellitus (T1DM) has increased recently; however, it is unknown how diabetes care attitudes affect late-life brain health. The Study of Longevity in Diabetes (SOLID) consists of 734 older adults with T1DM, reporting diabetes locus of control (dLOC), age of diabetes diagnosis and other demographics, history of hypoglycemic episodes, and depressive symptoms. Global and domain-specific (language, executive function, episodic memory, simple attention) cognitive functioning was assessed at in-person interviews. Cross-sectional associations between dLOC and cognition were estimated using covariate-adjusted linear regression models in pooled and sex-stratified models. In pooled analyses, a 1-point increase in dLOC (more internal) was positively associated with global cognition [β=0.05, 95% confidence interval (CI): 0.02, 0.07], language (β=0.04, 95% CI: 0.01, 0.07), and executive function (β=0.04, 95% CI: 0.01, 0.07), but not episodic memory or simple attention. However, in sex-stratified analyses, this effect was seen only in males and not females. In elderly individuals with T1DM, we found associations between dLOC and cognition overall and in men but not women. Underlying sex differences should be considered in future research or interventions on psychosocial characteristics for cognition.