Objective: To analyze the relationship between type 2 diabetes mellitus(T2DM)complicated by hypertension(HTN)and cognitive decline in middle-aged and elderly individuals, as well as the associated influencing factors. Methods: Middle-aged and elderly subjects who were treated at Sir Run Run Hospital Affiliated to Nanjing Medical University from September 2020 to September 2022 were enrolled and divided into four groups: patients with T2DM complicated by HTN(T2DMH group), patients with T2DM alone(T2DM group), patients with HTN alone(HTN group), and healthy controls(HC group). Clinical data were collected from the four groups. Cognitive and functional indicators were assessed using the Montreal cognitive assessment(MoCA), auditory verbal learning test(AVLT), trail making test(TMT) and digit span test(DST). Cognitive performance was compared among the four groups, and multivariate regression analysis was conducted to explore the associated influencing factors. Results: A total of 369 patients were enrolled in this study. These patients were assigned to four groups: the T2DMH group(n=105), T2DM group(n=106), HTN group(n=89), and HC group(n=69). No statistically significant differences were observed in age and years of education among the four groups(P > 0.05), indicating good comparability. The T2DMH group had higher HOMA-β than the T2DM group(P < 0.05), but DI did not differ between the two groups(P > 0.05); both were significantly lower than those in the HTN and HC groups(all P < 0.05). In terms of cognitive functions, the T2DMH group had worse performance in memory cognitive dimensions than the T2DM and HTN groups, and all indicators of cognitive domains in this group were significantly lower than those in the HC group(all P < 0.05). Cognitive function was significantly correlated with years of education, histories of T2DM and HTN, islet function and other indicators(P < 0.05). Multiple linear regression showed that years of education were positively associated with cognitive function; T2DM and HTN histories were significantly correlated with cognition, and alcohol consumption history as well as partial renal function parameters had varying degrees of correlation with cognitive performance(all P < 0.05). Conclusion: Patients with T2DM combined with HTN suffer from more severe metabolic disorders, organ damage and impaired islet function, accompanied by significant multidimensional cognitive decline, which is more severe than that in patients with isolated T2DM or isolated HTN. Disease duration of T2DM and HTN is independently and significantly associated with cognitive decline in middle-aged and elderly individuals. Higher education, better renal and islet function showed protective associations with cognition,though causal relationships require further validation in prospective cohort studies.