Thomasine Allen was appointed a missionary in 1915 and designated to Tokyo, sailing on August 25. She served as an educational-evangelistic missionary in Tokyo, Sendai and Morioka before going to Kuji in 1938 to begin to the rural ministry which brought wide recognition in the years to come. She was interned for two years beginning in 1941 and upon release worked among the the Japanese Americans at the Tule Lake Relocation Center until she returned to Japan in 1947. Her last trip home was in 1952-1953, after which she returned to Japan for good. Although she retired in 1958, she remained active in the work of the center and in the founding of a Junior College in 1970 in the town of Kuji. The Japanese government has twice given her high awards: the Imperial Fifth Order of the Sacred Jewel in 1958, and the Fourth Class Order of the Sacred Treasure in 1968. For the 50th anniversary of her arrival in Japan, she was given a personal congratulation from the U.S. Ambassador to Japan, Edwin O. Reischauer. In 1959, her alma mater, Franklin College of Indiana, gave her the honorary degree of Doctor of Humane Letters.