Tanzania has become one of the best choices for foreign direct investment (FDI) in East Africa and sub-Saharan Africa in general. The country has been pulling in an average of US$627 million a year and it is one of the continent's top foreign direct investment (FDI) performers. In 2011, the FDI value in the country reached $1,095,401,000.00 and the trend has been increasing. The booming of FDI is believed to have created jobs, increased incomes and contributed significantly to the national economy. Despite that, a large number of ordinary citizens have indicated dissatisfaction with this boom in FDI, which has caused a lot of conflict between investors and the surrounding communities where projects are taking place. In addition, environmental pollution has been observed in connection with a number of new investments. This paper assesses the contribution of environmental impact assessment (EIA) in informing the policy and decision-making process with regard to the boom in FDI in the country. The main focus of the study was to investigate the quality of the EIA undertaken and the extent to which they have influenced decision making with regard to the investments in Tanzania. This was done by reviewing EIA reports and having consultations with developers and regulatory authorities. The main findings are that, despite the existence of EIA for almost all development projects in the country, few of the mitigation measures proposed in the EIA reports are implemented by the developers. The study also revealed a number of EIA reports which were weak in terms of informing decision and policy makers to ensure that FDI would result in a win-win outcome. In addition, the enforcement and monitoring of environmental management plans by the authorities responsible was weak, partly due to inadequate resources.