Objective: A decline in dual-task postural control abilities increases the risk of falls, and older adults require more attention resources when performing dual-task postural control. This study, based on the dorsal attention network (DAN) and the default network (DN), explores whether multi-focus transcranial direct current stimulation (tDCS) can enhance dual-task postural control in healthy older adults. Methods: This study followed a randomized, double-blind, crossover design. A total of 30 healthy older adults were recruited, with 22 completing the experiment. Participants were randomly assigned to either tDCS or sham stimulation, with at least one week between the two interventions. The tDCS protocol aimed to increase the excitability of the DAN and inhibit the excitability of the DN, with a stimulation duration of 20 minutes (DAN+/DN-tDCS). The sham stimulation lasted only 1 minute (with 30 seconds at both the start and end). Before and after each intervention, Center of Pressure (COP) data were collected using the Kistler force table while subjects performed a single-dual task postural control test with eyes open and closed. The effects of the intervention protocols on various indicators of postural control were analyzed using a two-factor repeated-measures ANOVA (stimulus protocol × pre/post-intervention). Results: Participants completed the experiment without any notable adverse effects. In the eyes-open dual-task condition, significant interactions were found in both the total swing velocity (F = 5.72, p = 0.021) and the anterior-posterior swing velocity (F = 5.085, p = 0.029). Further analysis indicated that following the DAN+/DN-tDCS intervention, both the anterior-posterior swing velocity (p = 0.019) and the total swing velocity (p = 0.01) decreased. A significant interaction was also observed in the swing area dual-task cost under the eyes-open condition (F = 8.727, p = 0.005), with subsequent analysis showing a reduction in the swing area dual-task cost after the DAN+/DN-tDCS intervention (p = 0.038), while the sham stimulation resulted in an increase in swing area dual-task cost (p = 0.049). Conclusion: This study demonstrates that the DAN+/DN-tDCS intervention can significantly improve postural control performance in healthy older adults under dual-task conditions (reducing swing velocity, area, and dual-task cost), indicating that this approach has potential to improve postural control stability in older adults when performing dual tasks.