Understanding the magnitude, direction and agents of land use/land cover change (LU/LCC) are important for planning sustainable management of natural resources. To this end, this study assessed the trends of LU/LCC and its drivers in Western Ethiopia. Landsat images of MSS (1978), TM (1986, 1991 and 2010), ETM+ (1999) and OLI (2013 and 2016) were used to study the dynamics of LU/LCC. The land use/land cover (LU/LC) maps for each period were classified using a hybrid method by merging the outputs of supervised classification and intensive on-screen-digitizing techniques. The drivers of LU/LCC were studied using key informant interviews (KII) and focus group discussions (FGD). Four major LU/LC types namely forest, agriculture, shrub/grass, and settlement were identified with overall accuracies ranging from 91% to 94%. The result shows that forest was the dominant LU/LC type accounting for 69% in 1978 which later reduced to 13, 8.5 and 6.5 percent point (pp) in 1991, 2010, and 2016, respectively. Shrub/grasslands were also reduced by 11 pp from 2010 to 2016. Expansion of agricultural land was the major driver showing a radical increase by 13 pp between 2013 and 2016. Forest cover showed a reduction of 28 pp over the 38 years of the study period. In particular, 21.3%, 26%, and 16.6% of the forest was converted to shrub/grassland from 1986 to 1991, 1991 to 2010 and 2010 to 2016, respectively. But from 2010 to 2016, 19.13% of forest was converted to agriculture. The study showed that forest was first changed to shrub/grasslands and finally end up in agriculture showing that degradation is leading to deforestation. The result of FGDs and KIIs also showed that both small-scale subsistence agriculture and large-scale commercial agriculture are the major proximate drivers of deforestation in the study area. Population pressure from a multi-sourced and continued inflow of immigrants, lack of integrated institutional frameworks and unsustainable exploitations of forest products are the major underlying causes of the observed changes. Proper land use planning, legal backing, and institutional integration are key recommendations to sustain forest resources of the study area.