Tropical countries like Cambodia require information about forest biomass for successful implementation of climate change mitigation policies related to reducing emissions from deforestation and forest degradation plus (REDD+). This study investigates the potential of Phased Array-type L-band Synthetic Aperture Radar fine beam dual (PALSAR FBD) 50m mosaic data to estimate above ground biomass in Cambodia. The radiometric and terrain corrections were applied to reduce the topographic effects. Above ground biomass (AGB) was estimated using bottom-up approach based on field calculated biomass and backscattering (σ°) properties of PALSAR data. The relationship between the PALSAR σ° HV and HH/HV with field based biomass was strong with R 2 = 0.67 and 0.56, respectively. PALSAR estimated biomass shows good results in deciduous forests because of less saturation as compared to dense evergreen forests. The validation result shows high coefficient of determination R 2 = 0.61 with RMSE = 21 t/ha using values up to 200 t/ha biomass. There are some uncertainty because of uncertainty in the field based measurement and saturation of PALSAR data. Above-ground biomass map of Cambodian forests will provide information about the successful implementation of forest management practices for the REDD+ assessment and policies implementation at national level.