Although the neurobiological mechanisms underlying major depressive disorder (MDD) are not fully understood, accumulating evidence suggests an association between MDD and reduced levels of gamma-aminobutyric acid (GABA) in the brain. The present study used proton magnetic resonance spectroscopy (1H-MRS) with the Mescher-Garwood point-resolved spectroscopy sequence (MEGA-PRESS) to measure GABA levels in the pregenual anterior cingulate cortex (pgACC)/medial prefrontal cortex (MPFC). We also assessed resting-state functional connectivity using functional magnetic resonance imaging (rs-fMRI). Analyzing MRS data from 19 psychotropics free patients with MDD (14 female, mean age 30.7 years, age range 23-43) and 19 healthy control adults (13 female, mean age 32 years, age range 21-48), we found that GABA levels in the pgACC/MPFC were lower in the MDD group compared to the control group (t = 2.41, Cohen's d = 0.78, p = 0.02). To examine associations between mediofrontal GABA levels and whole-brain functional connectivity patterns, we performed multivariate pattern analysis (MVPA). This analysis identified a significant cluster in the left temporal pole for the interaction between GABA levels and groups. This suggests MDD-specific associations between mediofrontal GABA levels and whole-brain functional connectivity patterns from the left temporal pole. A post-hoc seed-to-voxel analysis with the left temporal pole seed revealed the significant interaction effect in the bilateral planum temporale, suggesting a significant group difference in the correlation between pgACC/MPFC GABA levels and functional connectivity from the left temporal pole to the bilateral planum temporale.