The right fronto-insular cortex (rFIC) is a core node of the salience network (SN) and plays a critical role in switching between the central executive network (CEN) and the default-mode network (DMN), an important function in cognitive processing. In the present study, we tested the hypothesis that the functional connectivity (FC) between the rFIC and the CEN and DMN may decrease with age in adults from youth to middle age given that the intra- and inter-network FCs of the three networks decline in aged people. We performed voxel-wise FC analysis based on resting state functional MRI data (171 subjects; 17-62 years of age) to investigate whether the FCs of the rFIC are associated with age in normal adults. We found age-related decreases in the positive FCs between the rFIC and the CEN and in the negative FCs between the rFIC and the DMN with and without atrophy correction. These findings suggest that the connection of the rFIC with the CEN and DMN is degraded even in middle-aged adults, which may influence the role of the rFIC in effectively switching between the CEN and DMN and may further affect cognitive function in these subjects.