Objective: Mild cognitive impairment (MCI) is a significant complication in elderly individuals with type 2 diabetes mellitus (T2DM). Although both T2DM and MCI can independently impair gait function, the specific patterns of gait control impairment under single-task (ST) and dual-task (DT) conditions, and the interaction between metabolic and cognitive dysfunction in the comorbid state remain unclear. This study aimed to investigate the gait characteristics of T2DM patients with MCI under ST and DT conditions, revealing the synergistic effects of metabolic and cognitive dysfunction on gait control. Methods: Forty elderly participants (≥60 years) were enrolled and categorized into four groups: HC (n=47), MCI (n=45), T2DM (n=45), and T2DM-MCI (n=48). Gait parameters were quantified using the OptoJump system under ST and DT conditions. Dual-task cost (DTC) was calculated to assess performance decline during concurrent cognitive-motor tasks. Results: Compared to ST, gait parameters significantly declined under DT conditions in all groups (all P<0.05), except for double support phase time in the HC group (P=0.09). The T2DM-MCI group exhibited the most severe gait impairment, with significantly lower step length (45.73 ± 1.63 cm), stride length (91.5 ± 2.84 cm), and walking distance (1843.18 ± 251.94 cm) compared to the HC group (P<0.05). Their DTC (34.2 ± 6.1%) was significantly higher than that of the single-disease groups (MCI group: 19.8 ± 4.1%; T2DM group: 14.6 ± 3.9%; P<0.01), and they demonstrated the most pronounced deterioration in spatiotemporal coordination under dual-task conditions (step length decreased by 23.7%, forward phase time increased by 42.9%). Conclusion: Patients with T2DM-MCI exhibit significant dual-task gait compensation deficits attributable to metabolic-cognitive interactions. A DTC threshold >20% may serve as a marker for compensatory failure. These findings provide a foundation for early screening and targeted intervention strategies in T2DM-MCI populations.