Mobility in daily life requires walking while performing a cognitive or an upper-extremity motor task (dual task walking). However, we only have a fair understanding of the dual task interference on gait performance, not mention on brain activity and its relationship with gait disturbance. In this study, we assessed the gait performance, including the walking speed, cadence, stride time and stride length, and brain activity in bilateral prefrontal cortices (PFC), premotor cortices (PMC), and supplemental motor areas (SMA) using the functional near-infrared spectroscopy (fNIRS) during cognitive and motor dual talk wailing. We aimed to provide better understanding of different dual tasks interference. Seventeen young adults performed the normal-pace walking (NW), walking while cognitive tasking (WCT), and walking while motor tasking (WMT) in their self-select pace. The repeated one way ANOVA was used to evaluate the effects of dual task on gait performance. To investigate the brain activity, the one-sample t test was employed to assess the change of relative HbO2 and Hb concentrations during different walking conditions. Additionally, the Pearson’s correlation coefficients (r) was used to examine the relationship between brain oxygen index (Oxy = HbO2 – Hb) and gait performance. All significant level was set at p< 0.05.Our results showed that compared to single task, both types of dual tasking caused significant decrease in walking speed and stride length. However, significant decrease in cadence and increase in stride time only showed in WCT. Regarding the brain activities, cerebral cortices activated according to the task demanding. Left PFC had the strongest and continuous activation during WCT, and only minor activation in the initial phase of NW and WMT. Differently, channels at SMA and PMC recorded increased oxygenations during both types of dual tasking (WCT and WMT) and only minor activations in the beginning of NW. According to the correlation analysis between brain oxygenations and gait data, we found that the activations of PMC and SMA played an important role in maintaining the gait performance on a certain level to prevent falling while performing multitasking during walking. We concluded that there are decrements in gait performance while executing either the cognitive or motor dual task in young adults, especially in gait speed and stride length. The cerebral oxygenations of PFC, PMC, and SMA altered distinctly according to the task demanding. Moreover, while performing dual tasks, PMC and SMA played an important role in maintaining the gait performance.