Soil sealing is one of the global anthropogenic impacts on the environment in the urbanized areas, responsible for irreversible changes in heat, water and nutrition exchanges between soil and atmosphere. A sealed soil loses a major part of its function including the capacity for carbon sequestration, therefore, a considerable depletion in soil organic carbon (SOC) is a highly likely result of urbanization. The soil sealing process and its effect on SOC stocks were analyzed in New Moscow for the period 1971–2017 and the depletion in SOC stocks was estimated for different types of soils affected by sealing in this region. The sealed area of the territory has increased by 6.7 times (from 30.8 km 2 to 208.8 km 2 ) since 1971 to 2017. The total estimated SOC losses in 1971, 1990 and 2017 were 262.7, 659.8 Gg and 1113.3 Gg correspondingly. The highest losses were obtained for the Alluvial acid soils, which lost up to 17% of initial areas and up to 12% of initial SOC stocks.