His only finished and published novel,
No-No Boy, deals with the aftermath of the Japanese-American internment during WWII and how this event divided the Japanese-American population after the war.
In his introduction to the novel, Lawson Fusao Inada writes of meeting Okada's wife, Dorothy, in La Grande, Oregon 1976:
Dorothy is a truly wonderful person. It hurt to have her tell us that "John would have liked you." It hurt to have her tell us that "you two are the first ones who ever came to see him about his work." It hurt to have her tell us that she recently burned his "other novel about the Issei, which we both researched and which was almost finished." It hurt to have her tell us that "the people I tried to contact about it never answered so when I moved I burned it, because I have him in my heart." [...] You could say John was "ahead of his time," that he was born too early and died too young.
Okada is the namesake of the Asian American ethnic themed dorm at Stanford University. Okada House is part of the Wilbur Hall Complex.