In this study, high-performance porous carbon for CO₂ adsorption was synthesized from pistachio shells and modified with urea to enrich nitrogen content in the porous structure. The effects of activation temperature, KOH-to-carbon ratio, and urea addition on the pore structure and CO₂ adsorption capacity of the porous carbon were investigated. Characterization was conducted using N₂ adsorption-desorption isotherms, scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FT-IR). Results showed that under preparation conditions of 700 °C, KOH-to-carbon ratio of 2, and 15 wt% urea concentration, the synthesized GAC-15-2-700 porous carbon exhibited a maximum specific surface area of 1395 m²/g, micropore volume of 0.505 cm³/g, and N-5 peak area ratio of 65.57%. It achieved a CO₂ adsorption capacity of 3.56 mmol/g. Nitrogen functional groups on the porous carbon primarily existed as pyridinic N (N-6), pyrrolic/pyridinic N (N-5), and quaternary N (N-Q), with the enriched micropores and high N-5 content being crucial for CO₂ adsorption.