The presence of forest park as green open space in densely populated urban areas and high traffic activities such as Jakarta, Bekasi and Bogor is important in absorbing CO2. However, the function of urban forests is limited because the studies were carried out on a small scale and at separate loci. This study aimed to estimate the biomass, storage and sequestration of carbon in five green open spaces located in Jakarta and Bogor areas. Biomass was estimated by non-destructive sampling for above ground biomass. The results estimated the forest park in Kanal Banjir Timur (KBT) absorbed CO2 of 1,000.01 ton/ha/year, the forest park at head office absorbed CO2 of 937.53 ton/ha/year, Mangrove Forest Park of Muara Tawar Bekasi absorbed CO2 of 46.10 ton/ha/year, and the Bukit Golf Pantai Indah Kapuk area absorbed CO2 of 147.91 tonnes/ha/year. Meanwhile the campus Forest Park of IPB University absorbed CO2 of 0.16 ton/ha. The value difference is influenced by parameters such as size or scale of sampling areas, number of stands, diameter, height, and coefficient value for each plant species. This study is expected to contribute in providing information and data on biomass, carbon content, and absorption in urban areas.