Mild traumatic brain injury (MTBI) may cause disruption of default mode network (DMN) in patients. We found differences in both resting state DMN connectivity and task-related deactivation between MTBI patients and healthy controls. Although no significant within-network difference was found in the DMN connectivity between patients and controls, there was increased extra-network connection to the left inferior frontal gyrus in the patients. Significantly more profound task-related deactivation was found in the patients, especially in bilateral IPCs. Increased task-related deactivation may imply the patients need more attention on performing the WM tasks. Furthermore, significant correlation between resting state connectivity and task-related deactivation of DMN was found in healthy controls and this rest-task correlation was disrupted in the patients.