The presence of green open space containing vegetation in urban areas plays a vital role in absorbing and storing carbon in biomass. Tanjungpura University (Untan) Pontianak has a green open area in the New Building of the Faculty of Forestry. This study aimed to describe carbon reserves stored in biomass above ground level (vegetation) in green open areas around the New Building of Faculty of Forestry Untan Pontianak. Data were collected using an inventory survey by non-destructive sampling, which includes recording with fully enumerated data collection on the type and diameter of trees with a continuous line plot system. The data were then analyzed using allometric equations to obtain biomass values. The results found as many as 56 species of trees with a total of 558 individuals dominated by Litsea garciae and Hevea brasiliensis. The results showed the amount of carbon stored at the tree level of 59.06 tons/ha (76.18%), pole level of 13.94 tons/ha (17.99%), and sapling level of 4.52 tons/ha (5.83%), with an average carbon stock of 77.52 tons/ha. Thus, the green open area could store 148.53 tons of carbon in tree biomass. Although it is a small area, this peatland ecosystem could accumulate peat in organic soil and its vegetation and should be managed as peatland forests. Therefore, proper management is essential, and hydrology management is needed mainly due to its nature. Keywords: allometric equation, biomass, carbon stocks, green open space