Land use change is a significant factor in environmental conservation and climate change which may be positive or negative depending on how it occurs. The study aimed at examining the land use changes that took place across River Nanyuki catchment from 1984 to 2010. Landsat images of the area were downloaded from USGS database and processed using CLASlite, a forest monitoring application developed by Carnegie Institute for Science (CIS) and ENVI software for land use classification and change detection. Four predominant land use classes were considered, namely forest, agriculture, uncultivated area, and water. Over the study period, the area was observed to have experienced different modifications, most notable being deforestation in the upper part of the catchment where Mount Kenya Forest extended with an overall accuracy of 80%. Most of the deforestation was understood to have taken place in the 1980s and 1990s with 2.5% forest depletion between 1984 and 1995.