OBJECTIVES: This study aimed to evaluate how cortical gray matter iron, measured using quantitative susceptibility mapping (QSM), changes in glioma patients and its relationship to cognitive scores. MATERIALS AND METHODS: This study included 121 glioma patients (45.42 ± 11.59 years; 61 females and 60 males) and 42 healthy controls (39.93 ± 10.37 years; 19 females and 23 males). The participants underwent cognitive assessment and brain magnetic resonance imaging using a 3D multi-echo gradient-echo sequence on a 3.0 T scanner. ITK-SNAP was used to measure the susceptibility values reflecting the iron content in the regions of interest (ROIs). We used analysis of covariance to investigate the differences in susceptibility between glioma patients and healthy controls in each brain region. Pearson's correlation analysis assessed the relationship between cortical magnetic susceptibility values and cognitive scores (MoCA). RESULTS: The frontal (p < 0.001), precentral gyrus (p < 0.001), postcentral gyrus (p < 0.001), parietal (p < 0.001), insular (p < 0.001), occipital (p < 0.001), and temporal cortices (p < 0.001) showed higher magnetic susceptibility in glioma patients than in healthy controls. There was a negative correlation between MoCA scores and magnetic susceptibility values in each brain region, precentral gyrus with significant differences (r = -0.253, p = 0.028). CONCLUSION: We quantified cortical magnetic susceptibility values reflecting the iron content in glioma patients using QSM and assessed participants' cognitive function using MoCA, and found that cortical iron deposition was increased in different brain regions and that cognitive decline in glioma patients may be associated with elevated iron content in the precentral gyrus.