Compost and biochar are widely used to improve soil quality by carbon sequestration. A laboratory experiment focused on evaluating the effectiveness of compost or biochar (from the same source) additions individually or in combinations on the soil organic mineralization (SOM), carbon stocks and some soil chemical properties after 45- and 90-days incubation was done. Six treatments were performed based on even mixture of biochar and compost as control without any addition (C), 1% compost (T₁), 1% biochar (T₂), 0.75 % biochar + 0.25 % compost (T₃), 0.50 % biochar + 0.50 % compost (T₄), 0.25 % biochar + 0.75 % compost (T₅). The results clearly indicated that adding mixture of biochar and compost significantly reduced gaseous emissions and build up soil carbon content. Soil organic carbon decomposition percentage (SOC) was at a minimum amount when the soil treated by 100% biochar (T₂) since it was 1.03 and 2.27% after 45 and 90 days, respectively. While it was at a maximum amount when the soil treated by100% compost (T₁) since it was 3.29 and 4.74% after 45 and 90 days, respectively. These results suggested that charring would considerably sequester soil C, especially at high application rates and in fine-textured soils. Biochar application is considered a new economic and environmental protection process as well as reducing carbon dioxide emissions.