The aim of this research was to examine the intrinsic functional connectivity of the brain reward system in individuals at risk for Internet Gaming Disorder (IGD). Here we focus on the ventral striatum (VS) and ventromedial prefrontal cortex (vmPFC), the key brain regions for reward hedonic processing and evaluation, respectively. Resting state functional magnetic resonance imaging was acquired from 18 young male participants with Internet-game overuse (IO) and 20 comparable normal subjects (NCs) to compare the intrinsic connectivities of the VS and vmPFC as the two seed regions. The group comparison was made between the functional connectivity maps of these two groups, where resting-state functional connectivity was examined using correlation analysis on the signal fluctuations of each voxel and that of a seed region. The results indicate that the vmPFC functional connectivity of the IO group was reduced relative to the NC group in the inferior parietal region, which is known for attention control and social evaluation. In addition, the IO groups exhibited increased negative functional connectivity between the VS and the ventrolateral prefrontal cortex, suggesting a compensatory mechanism via an inhibitory influence of cognitive executive function on the reward system. These observations suggest that impaired functional connectivity between reward processing regions and cognitive control regions in the frontal and parietal areas is a neurological risk factor for IGD.