Charles Montague Cooke Jr. was born in Honolulu, Kingdom of Hawai'i on December 20, 1874.
They built a grand estate in Manoa Valley, the Charles Montague Cooke Jr. House, also known as Kualiʻi, which is on the U.S. National Register of Historic Places listings in Oahu.
[4] Unlike his father and younger brothers such as Clarence Hyde Cooke who became financiers, his interests were in the field of malacology, the study of molluscs.
In 1905 he bought the extensive collection of shells from early evolution scientist John Thomas Gulick.
He worked with Henry Augustus Pilsbry to identify species of snails in the Hawaiian Islands.