•Porous carbon microspheres was used to load methylated polyethylenimide.•mPEI@NCMs can be used as a novel adsorbent for highly-efficient SO2 capture.•mPEI@NCMs showed efficient selection and reversible adsorption for SO2. Solid-supported materials are extensively utilized for SO2 capture. Polytertiary amine compounds, which are abundant in tertiary amine groups, efficiently capture SO2. In this study, we propose the loading of methylated polyethylenimide (mPEI), which is rich in tertiary amine groups, into chitin-derived carbon microspheres (NCMs), which have a robust pore structure and large surface area. The produced adsorbent (mPEI@NCMs) showed good performance for capturing SO2. Further, the adsorption capacity of mPEI@NCMs for SO2 at 25 °C and 1 bar was 12.23–18.12 mmol/g, whereas at 25 °C and 0.01 bar, it was 4.58–6.96 mmol/g. The mPEI@NCMs sample showed good selectivity for adsorbing SO2 from mixtures containing N2 and CO2. Furthermore, mPEI@NCMs showed a good reversible adsorption capacity for SO2.