Objective <p>Humans use their motor and cognitive functions simultaneously while voluntarily performing real-time selective motor movements in daily life. This study aimed to investigate the effects of dual-task training on upper extremity motor skills and daily living activities in patients with Parkinson’s disease.</p> Methods <p>The patients were randomized into two groups. One of the groups (Control) received a conventional physiotherapy program, while the other group (Dual-Task) also performed a cognitive-based dual-task intervention in addition to traditional rehabilitation. All rehabilitation programs were continued for 60 × 5 × 6&#xa0;min/day/week. The assessments were performed twice: The two subsections of the MDS-Unified Parkinson’s Rating Scale (MDS-UPDRS II and III), Box Block Test (BBT), and Parkinson’s Disease Questionnaire-39 (PDQ-39).</p> Results <p>There was no difference in any parameter between the groups, neither baseline nor after treatment (<i>p</i> &gt; 0.05 for all). In the within-group assessments, the amount of change was higher in the MDS-UPDRS II and III sub-dimensions scores of the Dual-Task group. An increase was observed in the BBT results of both groups compared to pre-treatment (<i>p</i> &lt; 0.05 for all). While the PDQ-39 score of the Dual-Task group improved by approximately 18% (<i>p</i> = 0.003), no change was detected in the control group (<i>p</i> = 0.413).</p> Conclusion <p>Dual-task interference maintained throughout rehabilitation may enable the development of motor-cognitive functions required by individuals with Parkinson’s disease to perform daily living activities. For this reason, including dual-task training in rehabilitation to manage upper extremity impairment due to Parkinson’s disease may be helpful to maximize gains.</p> Trial registration <p>This study was registered to clinicaltrials.gov with NCT06803212 ID (01.30.2025).</p>