Objective: To explore the effects of dual task (DT) training on DT gait performance and cognitive function in individuals with Parkinson disease (PD) and to examine factors that might influence the effects of DT training. Data Sources: PubMed, Wiley Online Library, Cochrane Library, CINAHL, and Medline were searched for articles published from January 2006 to December 2021. Study Selection: Randomized controlled trials comparing DT training with usual care or general exercise were included. Data Extraction: The outcomes studied were DT gait parameters including speed, step and stride length, cadence, step and stride time variability, dual-task cost on gait speed, and Trail Making Tests presented as standardized mean differences (SMDs). The Grading of Recommendations, Assessment, Development, and Evaluation was used to evaluate the quality of evidence. Data Synthesis: Ten randomized controlled trials with 466 participants were included in the meta-analysis. The included studies presented, in general, with a low to high risk of bias. Meta-analyses used a random-effects model for all analyses. The meta-analysis showed the DT training effects on DT gait speed (SMD=0.825, P=.012), DT step and stride length (SMD=0.400, P=.015), Trail Making Tests-part A (TMT-A; SMD=0.533, P=.010), and Trail Making Tests-part B (SMD=0.516, P=.012) compared with the control group. Only the effect on TMT-A was maintained at the follow-up assessment. The results of meta-regression showed that participants with slower initial single task gait speed improved more after DT training on DT step and stride length. Conclusions: The DT training improved more in DT gait speed with moderate-quality evidence as compared with usual care or conventional physical training in individuals with PD. The beneficial effects of DT training on DT step and stride length, attention, and executive function were also demonstrated in this meta-analysis. Furthermore, the improvement in the DT walking step and stride length was related to the participant's initial single task gait speed.