This study aims to determine the role of UNEP in environmental diplomacy, with particular focus to East Africa. Over the last two decades, there were mainly localized issues of the environment such as urban air pollution, waste disposal and unsafe water supplies. These problems still exist mainly in developing countries which are now industrializing. It is evident that there is no country or group of countries, which can solve these planetary problems by themselves, including the powerful developed nations of the North. This therefore calls for an international body dealing with environmental issues in providing leadership, negotiation, implementation of policies made as well as accountability in solving these environmental issues. This study therefore is designed to determine the role played by this international body, UNEP, in the provision of leadership, negotiation power, policy implementation and accountability in environmental diplomacy. This study will adopt a case study research design. Data will be collected from secondary sources. This will involve reviewing material sources in the form of journals, books and reports. The collected data will be analyzed thematically by constructing themes that will help discuss the role of UNEP in East African environmental diplomacy. Data will be presented in a narrative form which will be derived from evidence secondary sources that will be used to support and illustrate themes.