He lived in Boyle Heights, graduating from Roosevelt High School in East Los Angeles.

From 1953 to 1956, Tashima served in the United States Marine Corps, and was honorably discharged with the rank of sergeant.

Tashima returned to private practice in 1977, as a partner at Morrison & Foerster, in Los Angeles.

His service terminated on January 8, 1996, due to elevation to the Ninth Circuit.

[4] Tashima was nominated by President Bill Clinton on April 6, 1995, to a seat on the United States Court of Appeals for the Ninth Circuit vacated by Judge Arthur Alarcón.