The Colombo Museum as it was called at the beginning was established on 1st January 1877. It founder was Sir William Henry Gregory, the British Governor of Ceylon (Sri Lanka) at the time.
The Royal Asiatic Society (CB) was instrumental in bringing to the notice of Gregory on his appointment as Governor in 1872 the need for a public museum with much difficulty the approval of the legislative council was obtained within a year. The Architect of the Public Works Department, J.G. Smither was able to prepare the plans for new structure on Italian architectural style. The construction was completed in 1876 and the Museum commenced it functions in the following year.
The Authorities of the museum took various steps to display the cultural and natural heritage of the country for this purpose.
With the development of the museum to international level, it earned the status of a national museum during the period of Dr. P. E. P. Deraniyagala. He was able to open up branch museums in Jaffna, Kandy and Ratnapura and a full - fledged Department of National Museums was established in 1942 under the act No. 31. The extension of the number of branch museums has now increased to nine and in addition a school science programme and a mobile museum service are also in operation.