The article analyzes the spatial pattern of alterations in land cover in the municipalities directly affected by the Tucurui reservoir. This analysis was carried out by using Landsat satellite images. The mapping of the land cover classes and the quantitative characterization of the classes present in the region were carried out between the start period of the II phase and the conclusion of the construction of the Tucurui hydroelectric power plant. The study was carried out in two phases, the first one corresponds to the application of the linear model of mixing in Landsat-TM and ETM+ segmented images, executed for the mapping of the land cover classes. The second, corresponds to the calculation of landscape metrics, with the purpose of quantitatively characterizing the classes. The results revealed alterations in the spatial pattern of forest cover around the Tucurui Lake. The municipality of Novo Repartimento was the one that presented the largest expansion of deforested areas and is also the municipality that houses most of the reservoir. The high level of fragmentation is associated with highways and country roads in the region, which allow connectivity between urban spots, facilitating access to new areas and conversion of forests into large areas for agribusiness.