Foster Garden traces its beginning to 1853 when Queen Kalama leased a small area of land to William Hillebrand, a young German doctor. A botanist as well as a physician, he and his wife built a home in the upper terrace area of the present garden. The magnificent trees which now tower over this area were planted by him. After twenty years in Hawaii, he returned to Germany and produced the excellent botanic treatise, Flora of the Hawaiian Islands (1888).

The Hillebrand property was later sold to Thomas (Captain) and Mary Foster who added to it and continued to develop the garden. Upon Mrs. Foster's death in 1930, the 5.5 acre site was bequeathed to the City and County of Honolulu as a public garden. The Foster Botanical Garden opened to the public on November 30, 1931, with Dr. Harold Lyon as its first director. Over a span of 27 years, Dr. Lyon introduced 10,000 new kinds of trees and plants to Hawaii. The Foster Garden orchid collection was started with Dr. Lyon's own plants.

Through purchases by the City and gifts from individuals, under the directorship of Paul R. Weissich (1957-89), Foster Garden expanded to over 13.5 acres. In addition to being a pleasant place to visit, Foster Botanical Garden is a living museum of tropical plants, some rare and endangered, which have been collected from throughout the world's tropics over a period of 150 years.

More than 75,000 visitors view the garden annually. Guided tours are given to thousands of school children as well as visitors from around the world. Honolulu's botanical garden system has broadened to other sites and now includes, in addition to Foster Botanical Garden, four other gardens on Oahu.

The Director of the Honolulu Botanical Gardens is Winifred N. Singeo.