Over-grazing, bush encroachment and alien species invasion are having negative impacts on livestock production in the rangelands of Sub-Saharan Africa, thus threatening rural livelihoods in the region. Leaf area index (LAI) can be used as an indicator or an early warning signal of changes in rangeland conditions. The aims of this study were to (i) assess the accuracy of the existing MODIS LAI product for key land cover classes and biomes in South Africa and (ii) assess the accuracy of LAI retrieved by the inversion of PROSAIL radiative transfer model. The MODIS LAI estimates were particularly poor for grassland and Karoo biomes for the period under investigation (November 2012 to February 2013). More accurate estimates of LAI values (RMSE = 0.9) across three major biomes were generated by inverting model outputs from PROSAIL radiative transfer model on MODIS imagery.