Lagos mega-city located on the narrow Coastal flood plain of the Bight of Benin of South-Western part of
Nigeria is a continuous and rapid urbanized society. The rapid urban growth has affected the city planning thereby
hindering its water security. This study assesses the implications of urbanization and climate change on water
security in Lagos mega-city. The study traces its findings through historical information on how urbanization trends
have influenced the mega-city status. It also examines and correlates secondary data from both qualitative and
quantitative sources on water security in Lagos. It identifies water security in the mega-city in terms of threats to
the environment such as in flooding relating it to urbanization tendency and climate change vulnerability. It also
examines water security threats in Lagos mega-city in the case of inadequate water supply in the metropolis
relating it to its urbanization tendency and climate change security threats. It further investigates urbanization
trends, water and climate security and threats alongside the human security components. The study identifies
different parts of the city that are prone to the risk of water and climate change security. On the final note, the
study suggests ecosystem approach as the foundation for workable mega-city environmental governance which is
the key to the sustainable management of Lagos water and climate security.