Dual-task walking is challenging for people with Parkinson disease (PD). Gait performance worsens while executing dual tasks, possibly due to a decline in executive function (EF). This study aimed to investigate the effects of dual-task training on EF and dual-task cost (DTC) in people with PD and to explore whether training-induced changes in EF were associated with changes in DTC. This study was a randomized controlled trial. A total of 28 people with PD participated. Participants were randomly assigned to the experimental group (dual-task training) and the control group (treadmill training). Both groups received a total of 16 training sessions during the 8weeks. Assessments were conducted at baseline and postintervention. Primary outcomes included EF and dual-task cost. Significant time-by-group interactions were found in executive function and DTC. The experimental group showed significant improvement in frontal assessment battery (FAB), trail-making test (TMT) part A, Stroop color and word test (SCWT), and DTC on speed in cognitive dual-task walking. There was a moderate to high correlation between the change values of the FAB, TMT part A, SCWT, and the change values of DTC in cognitive dual-task walking. Compared to treadmill training, dual-task training resulted in greater improvements in EF and DTC. Training-induced changes in EF were linked to changes in DTC when walking while performing a cognitive task but not when walking while performing a motor task. For more insights from the authors Supplemental Digital Content available at http://links.lww.com/JNPT/A485.