Chrey Bak River catchment is recognized by the Royal Government of Cambodia (RGC) as an important area for agricultural investment and development. As a consequence, the catchment has experienced intensive land use and land cover changes. The objectives of this paper are to investigate the land use change in Chrey Bak River catchment during 2010-2040 and to define the underlying factors/decision variables that affect to land use change and to use CLUMondo model for the simulation and predicton. Data of initial land use map (2010) and trend data of the change in land use of Cambodia (2004-2013) with Annual Growth Rate method were used to project the areas of each land use type until 2020. The results of the simulation indicate that during the period of 2010-2040, water bodies still remain constant with an area of 27 ha while built-up areas would be expanded by 142% (from 251 ha to 608 ha). In addition, grasslands and shrublands areas would be increased respectively by 7% (from 4151 ha to 4430 ha) and by 8% (from 25254 ha to 27240 ha). Furthermore, the agricultural expansion would happens significantly in the study area and it would be grown up by 19% (from 25763 ha to 30738 ha). In contrast, there would be a rapid decline in Forest covers by 47% (from 16083 ha to 8486 ha). This study also provides a model validation method named “Kappa Statistics” which is very practical for land use change comparison. On the basis of the results of this research, it can be concluded that land use change prediction of Chrey Bak River catchment by using CLUMondo model can suitably serve as an indicator of the direction and magnitude of change in the future. Land use change modeling is now highly dynamic field of research with many new developments and the results of land use models are important to evaluate policy options and assess the impact of land use change on natural and socio-economic conditions.