Abstarct: This Ph.D. thesis investigates the impact of carbon dioxide (CO2) and methane (CH4) adsoption and emission on the engineering properties of coal and the stability of underground mines. Considering the importance of the coal industry and the associated environmental and safety challenges, the development of optimal extraction methods and coal gas management is essential. In this thesis, the influence of CO2 and CH4 adsoption and emission on the uniaxial compressive strength, elastic modulus, and axial strain of coal samples was investigated under various laboratory and macroscopic conditions. The results showed that CO2 adsorption had a more significant negative impact on the engineering properties of coal, substantially reducing its strength. Specifically, CO2 adsoption and emission at injection pressures of 15 and 30 bars reduced the maximum compressive strength of coal samples by 57.80% and 57.15%, respectively, and decreased the elastic modulus by 77.67% and 22.03%, respectively. In contrast, CH4 adsoption and emission at injection pressures of 15 and 30 bars reduced the maximum compressive strength of coal samples by 27.9% and 41.7%, respectively, and decreased the elastic modulus by 18.06% and 19.91%, respectively. This reduction in engineering properties is a function of gas injection pressure, coal type, inherent fracture structure and orientation, moisture content, and other influential factors. baxsed on the results of this thesis, the stability of coal pillars exposed to CO2 is reduced, and this issue should be given special attention in the design and implementation of CO2-enhanced coal bed methane (ECBM) recovery methods, as well as in CO2 sequestration projects in coal mines. It is important to note that the release of CH4 from undegassed and degassed coal seams also reduces coal strength and increases the likelihood of coal dust explosions, outbursts, and coal pillar instability. The findings of this thesis emphasize the importance of a thorough investigation of the effect of gases present in coal mines on their stability and highlight the need for further studies in this area.