After the 30-year long civil war was over, the Government of Sri Lanka commenced an accelerated programme to develop the Northern Province. If not carefully planned, such a programme will result in the loss of biodiversity and the consequent loss of services that ecosystems provide humans. Therefore, documenting the biodiversity found within coastal, nearshore and offshore islands of the Northern Province was identified as a need that would help both planners and conservation biologists alike. This report presents the results of a rapid biodiversity assessment of a 949 km stretch from Mannar to the Kokkilai Lagoon, including 22 coastal islands, five coastal stretches and four lagoons, extending across four districts (Jaffna, Mannar, Kilinochchi and Mullaittivu), 20 Divisional Secretariats Divisions and 264 Grama Niladhari Divisions. For terrestrial ecosystems, assessments were carried out during November 2015 and March 2016, and for marine surveys in the coastal waters of Palk Bay and Palk Strait, during November 2015 and March 2016.