Born in Long Beach, California, Okamura gave his first solo show for his kindergarten class in his parents' garage.  Okamura continued his education (13 years later) at the Art the Institute of Chicago.   Arthur was very prolific and successful during the late 1950s and the 1960s, often painting 100 canvases a year. He used natural forms and landscapes changed into abstractions-sometimes totally non-objective ones.  Due to the pressure of the art business, Okamura chose to stop painting for two years during the late '60s. He moved to Berkeley, California, where he rediscovered his love of drawing, and began to illustrate books of poetry by Robert Creeley, Robert Bly and Steve Kowit.
During W.W. II, Okamura was held in the concentration camp in Amache, Colorado. Years later, he had a role in a John Korty film about the internment camps. He played an artist asked to sketch the deceased, as no cameras were allowed in these concentration camps.

Okamura taught at the Art Institute of Chicago, as well as the California College of Arts and Crafts. He has blended East and West in his life and art.  Some paintings resemble the Zen practice of sand raking and others the circular pattern of the mandala.