The effective connectivity can reveal the causal relationships between nodes of the Default Mode Network (DMN), which may reveal any impairment to the network following moderate traumatic brain injury (MTBI). Eight sub-acute MTBI patients and eight controls were recruited for this study. The results indicated that effective connectivity (EC) within MTBI group was higher in number and strength compared to the controls. Moreover, the network hubs within DMN are associated with increased connection strength in MTBI group. The ECs in MTBI are also largely influenced by top-down backward connections. In conclusion, the network reorganization within the DMN reflects the effect of MTBI and may subsequently impair other brain functions. This knowledge can be used to correctly identify the patient for appropriate trauma management.