Urban growth contributes to land use and land cover changes in protected forest reserves primarily through conversion of peri-urban areas into settlements, agriculture and unsustainable harvesting of ecosystem services to meet demands of the population in the peri-urban and urban areas. It has been widely argued that increased anthropogenic activities have altered the forest cover for Pugu and Kazimzumbwi Forest Reserves. Nonetheless, these arguments are little supported by quantitative data. A study on the dynamics of land use and cover changes in the Pugu and Kazimzumbwi Forest Reserves therefore investigated long-term changes that have occurred as a result of human activities in the areas for the periods 1985-1995 and 1995-2010. Landsat TM and ETM+ images were used to locate and quantify the changes using remote sensing and GIS techniques. Perceptions of local people on historical changes and drivers for the changes were also collected from three neighbouring villages and integrated in the assessment. The analysis was augmented by statistical analysis of 30 years historical rainfall and temperature records from Dar es Salaam and Kisarawe Climatic Stations. The study revealed remarkable decline in closed forest area in the latter period at -1.7 ha/year for Kazimzumbwi Forest Reserve (KFR) and -1.53 ha/year for Pugu Forest Reserve. The woodland variably decreased during the 1985 and 1995 period for both PFR and KFR but increased for PFR and decreased for KFR in the latter period. Unlike for closed forest and woodland, the cultivated land and built up area increased between the two periods for both forests reserves, while other covers variably increased or decreased between the years. The peoples’ perceptions and drivers for the changes are presented and discussed together with the land use and land cover change analysis. The study concludes that, there has been remarkable changes in land use and cover in the catchment and these require concerted actions to reverse the changes and enable the forest reserves contribute to REDD initiatives.