Colombo city, the commercial capital of Sri Lanka and also a popular tourist
destination is currently under a redesigning program coupled with landscaping
activities. Therefore it is important to investigate the spatial distribution of the
green cover and its change over the time so that the findings can effectively be used to identify priority areas for restoring and revitalizing the greenery of the city. This study was conducted on mapping the green cover in all 47 wards of Colombo city for the years 1956, 1982, 2001 and 2010 by analyzing aerial photographs and IKONOS maps using Geographic Information Systems. Investigations were further extended to identify the vegetation cover% and its change in each ward during the 54 year study period. According to the results, the green cover of Colombo city declined from 35.67% to 22.23% from 1956 to 2010. In 2010, the highest green cover (49.65%) was reported in Narahenpita and only three other wards (Kirillipone, Cinnamon Gardens, and Thimbirigasyaya) had green cover over 30% of the total land extent. In contrast, the green cover was less than 10% for ten wards, i.e., Kochchikade North, Kochchikade South, Grandpas North, Masangasweediya, Panchikawatte, Fort, Gintupitiya, New Bazaar, Maligawatte, and Aluthkade East. Under the current redesigning plans, those ten wards should be given the priority to increase the green cover to re-establish a healthy environment. Expansion of built-up areas and road network can be surmised as major reasons for the gradual reduction of green cover in Colombo city.