Kajiro Yamamoto attended Keio University where he helped form a film appreciation society.
Yamamoto Kajiro first appeared in film in 1921 as an actor opposite Yoshiko Okada, but that only earned the wrath of his family, who disowned him. He worked as an actor on the stage, joined Nikkatsu as an assistant director, and finally made his directorial debut in 1924 at Toa Kinema. After working at Nikkatsu again, he was lured to Photo Chemical Laboratories (P.C.L.) in 1934, where he first made a name filming the comedies of Kenichi Enomoto. When P. C. L. became the Toho company, Yamamoto helmed realist dramas such as Tsuzurikata kyoshitsu and Uma (starring Hideko Takamine), and war films such as Hawai Mare oki kaisen.
After World War II, he continued directing films, but increasingly worked in television and radio. Yamamoto is also a witty writer and has written a book on the film industry.