Marine nonindigenous species (NIS) are one of the most significant threats to oceans. This article discusses the marine bioinvasions in Sri Lanka. Sri Lanka is highly vulnerable from marine bioinvasions considering its strategic location well connecting the east-west shipping route with a high marine traffic and high marine/coastal pollution. Many of the commercial ports/harbours are also located close to marine sensitive areas. However, the Marine Pollution Prevention Act No. 35 of 2008 implemented by the Marine Environmental Protection Authority (MEPA) has unclear provisions for ballast water management and does not address other vectors of NIS. There is an urgent need for the management of marine NIS followed by NIS monitoring and observations (which is currently inadequate).