A Nikkeijin (first-generation Japanese-American), Shimada emigrated to the United States in the early 1930s to follow in the footsteps of his idol Sessue Hayakawa, where he began acting in theatre before finding a steady career playing supporting roles in Hollywood films.

After being interned during World War II, Shimada found a career resurgence starring opposite Humphrey Bogart in the 1949 film, Tokyo Joe.

He enrolled in acting courses at the studio of Katherine Hamil, and subsequently starred in a student production of The Flower of Edo, a one-act play about Japan.

In June 1931, he headlined a class show in Los Angeles's Jinnistan Grotto theater, performing scenes from Melchior Lengyel's play The Typhoon.

Shimada's character Dr. Nogi (based on the celebrated Japanese-born bacteriologist Hideyo Noguchi) has special powers to resist pain and treat illness.

Shimada's last prewar role of importance was in the 1939 thriller Mr. Moto's Last Warning, in which his character was a decoy who impersonated the eponymous Japanese spy (played, ironically, by a non-Japanese, Austrian-born actor Peter Lorre).

He dreamed of relocating to New York and establishing himself in the Manhattan theater world, but was unable to get away from the West Coast in time before resettlement was "frozen" in late March.

The Guild performed in mess halls, putting on skits and comic sketches of camp life, including "Coming to Boilton" and "The Blockhead's Nightmare".

In fall 1942, the Guild announced a forthcoming original three-act comedy, "Postonese", depicting life in camp, to be written and directed by Shimada and his fellow actor Wilfred Horiuchi.

Worse yet, during the hiatus of the construction, the Guild's original actors went into other jobs or began leaving camp, and Shimada was forced to re-cast his show—he thought of recruiting high school students.

Armed with a certificate from the American Red Cross that authorized him to give classes in swimming and lifeguard training, he joined Captain Tetsuo Sakamoto to champion a "build a pool" project.

"Mr. Shimada's proven leadership of the younger men, and his sympathetic understanding of the needs and interests of the older people, will be of great value to the enjoyment and harmony of the residents of Unit I," Powell told the Poston News-Chronicle.

Even after the end of World War II and the return of Japanese Americans to the West Coast, the other Nikkei actors who had worked in Hollywood in the 1920s and 1930s (apart from Sessue Hayakawa) would disappear from view.

In summer 1945, while still confined at Poston, Shimada was cast as a Filipino scout in a war propaganda film for 20th Century Fox, to be entitled American Guerilla in the Philippines.

Shimada's role was that of Yuan, a young Chinese man who returns to his family in China after spending several years studying in the United States, and clashes with his wife because of her traditional ways.

When the show played New Orleans in February 1946, local critic Gilbert Cosulich described Shimada's lead performance as "intelligently though a bit stiffly portrayed."

The two started work on Tokyo Joe, a new motion picture starring Bogart that would be set in Occupation-era Japan, and sought Japanese actors to play in it.

The producers located Sessue Hayakawa, by then long absent from Hollywood and living in France, and he agreed to make a comeback role as the main villain.

Bogart's character Joe Barrett, who had run a bar in Tokyo before the war, comes back to occupied Japan after 7 years away to take care of some unfinished business.

Shimada later stated that Tokyo Joe had been his most enjoyable film experience, as even people who did not know his name recognized him as the man who had beaten Bogart in a fair fight.

In The Bridges at Toko-Ri he plays a man who brings his wife and children to a Japanese bath and is surprised to find William Holden and his family already in the tub.

In House of Bamboo (1955) Shimada played the uncle of Yoshiko Yamaguchi's lead character—the film also offered him his first chance to work together with his childhood idol Sessue Hayakawa.

There Shimada plays Sen-Sei, a blind instructor and mentor to the geisha Sumi who is a master of the Japanese musical instrument called the koto (in fact performed by Kimio Eto).

Sen-Sei has a lengthy conversation with Bob, explains to him with kindness how badly he's been behaving, and persuades him to show faith in Japanese justice and his financée's love by surrendering himself to the authorities, rather than letting himself be smuggled out of the country.

Mr. Osato wishes Bond well as he departs his office, then waits a few seconds, turns to his "Confidential Secretary" Helga Brandt (Karin Dor) and utters the succinct icy command: "Kill him!"

In his later years, Shimada appeared on a number of episodes of popular television series, including I Spy, Mannix, Have Gun – Will Travel, The Doris Day Show, and The Six Million Dollar Man.