Many countries worldwide are experiencing natural disasters that have not been experienced in the past owing to abnormal weather caused by climate change, resulting in considerable economic damage and human casualties. Global warming, which is the increase in Earth’s temperature due to the greenhouse effect primarily caused by carbon emissions to the atmosphere, is considered as the main cause. Thus, various international agreements are being promoted to reduce carbon emissions. The Republic of Korea (ROK) is also abiding with these international agreements and enacting and enforcing related and fundamental laws in response to international trends. To reduce carbon emissions, the management and composition of existing and new carbon sinks are being highlighted, and urban park green areas play an essential role as existing carbon sinks. Research is needed to understand how urban parks can contribute to carbon neutrality and the importance of local government units that manage these urban parks. Therefore, in this study, we aim to quantitatively analyze the current status of CO2 storage and absorption of trees in urban parks on the basis of tree survey data obtained from representative urban parks located in Daejeon-si, the target site of this study. The methodology for analyzing the amounts of CO2 storage and absorption was applied in two ways by referring to previous studies, and the reliability of the results was reviewed to confirm the appropriate methodology. In addition, on the basis of the amounts of CO2 storage and absorption per unit area of the park derived through analysis, the amounts of CO2 storage and absorption of trees in urban parks for the entire city of Daejeon-si were estimated. As a result of this study, the amounts of CO2 storage and absorption of 1931 ha of 557 established parks, parks under construction, and unconstructed parks in Daejeon-si were calculated as 492096 tCO2/ha and 18498 tCO2/ha/y, respectively. The storage and absorption of CO2 per unit area in this study are expected to be used as data for climate change response, carbon neutrality measures, and decision-making.