Yoshiko made her debut as an actress and singer in the 1938 film Honeymoon Express. She was billed as Li Xianglan; pronounced Ri Koran in Japanese. The adoption of a Chinese stage name was prompted by the Film company's economic and political motives鈥攁 Manchurian girl who had command over both the Japanese and Chinese languages was sought after. From this she rose to be a star and Japan-Manchuria Goodwill Ambassadress. Though in her subsequent films she was almost exclusively billed as Li Xianglan; she indeed appeared in a few as "Yamaguchi Yoshiko." Many of her films bore some degree of promotion of the Japanese national policy (in particular pertaining to the Greater East Asia Co-prosperity Sphere ideology).

At the end of World War II; she was arrested by Chinese government for treason and collaboration with the Japanese. However; she was cleared of all charges; and possibly the death penalty; since she was not a Chinese national; and thus the Chinese government could not try her for treason. And before long in 1946; she settled in Japan and launched a new acting career there under the name Yoshiko Yamaguchi.

In 1974; she was elected to the House of Councillors (the upper House of the Japanese parliament); where she served for 18 years (three terms).