We demonstrated CRP sensing using SCM-GFETs. An array of SCM-GFETs functionalized with anti-CRP mAb and non-functionalized GFETs was integrated onto a chip, and differential measurements were performed to eliminate background changes and improve the measurement reliability. The FET response was consistent with the fluorescence images, which showed specific adsorption onto the anti-CRP mAb. Additionally, the estimated KD agreed with a previously reported value, providing further support that the results were attributed to the specific adsorption of CRP. In contrast, signals from GFETs without decoration were buried in the noise because of nonlinear electrolytic screening, highlighting the significance of surface-charge modulation. The LOD of the system was estimated to be 2.9 nM, which can be improved through further optimization of the surface charges to match the target applications. In FET biosensors, charge screening in an electrolyte solution remains a major limiting factor for sensitivity, thereby restricting the application window for FET sensors. Our approach can pave the way for further applications of GFET biosensors.