The impact of cognitive load on individuals with motor impairments is poorly understood. To better understand the impact of cognitive load during activities of daily living, we measured brain activity from a dry EEG headset as participants attended to an auditory stimulus paradigm during sitting, standing, and walking. The P3 event-related potential, which is sensitive to cognitive load, was extracted from EEG signals in each condition. Results showed that P3 was significantly lower during walking compared to sitting (p = .039), indicating that cognitive load was higher during walking compared to the other activities. No significant differences in P3 were found between sitting and standing. Head motion did not have a significant impact on the measurement of cognitive load. These results encourage the use of a dry EEG system to further investigate cognitive load during dynamic activities in individuals with and without motor impairments.