In this particular work, a simple, cost-effective and single step process to synthesize magnesium oxide modified nitrogen doped porous carbon (MgO/NMC) by thermal decomposition technique has been elaborated and its high-pressure performance as CO2 and CH4 gas adsorbent is demonstrated. The uniformly distributed porous network in the samples was identified from the morphological studies by FESEM and TEM. Elemental analysis and XPS studies were carried out to understand the Mg and N contents. It has been observed that MgO/NMC shows appreciably high CO2 (30 mmol g−1 at 20 bar and 25 °C) as well as CH4 (12 mmol g−1 at 30 bar and 25 °C) adsorption capacity. The surface modification of the samples (caused by the presence of MgO nanoparticles) along with high surface area and good porosity containing interconnected macro-/ meso-/ micropores synergistically improves the adsorption capacity. In addition, high nitrogen content in the nanocomposite enhances the number of basic adsorption sites thereby increasing the gas adsorption capacity. The effect of concentration of MgO on gas adsorption capacities has also been investigated from the adsorption isotherms. The moderate heat of adsorption, as well as good recyclability and selectivity at high pressure, shows that MgO modified nitrogen doped porous carbon composite can be a promising candidate for both CO2 capture and CH4 storage. © 2018