Abstract: Objective To investigate the effects of α-lipoic acid on the cognitive function of patients with type 2 diabetes mellitus. Methods A total of 140 patients with type 2 diabetes mellitus were divided into two groups, according to their treatment with or without α-lipoic acid. Patients in Group A (n=70) received conventional diabetic therapy, while those in Group B (n=70) were intravenously injected with α-lipoic acid daily in addition to conventional diabetes therapy. Then, the Montreal cognitive assessment (MoCA) was performed to evaluate the cognitive function of these patients before and 30 days after treatment. Results Before treatment, the cognitive function score of Group A was (23.93±3.45) on average, while the average cognitive function score of Group B was (24.90±3.66), which were not significant different between the two groups (P>0.05). After treatment, the cognitive function score of Group A was (22.91±3.74) on average, which was significantly lower than the average cognitive function score of Group B (26.77±2.27). Conclusions α-Lipoic acid has a protective effect on the cognitive function of patients with type 2 diabetes mellitus.