Pierce was born in Germany and raised in Riverside County, California. His father worked as a public school custodian and his mother was a homemaker. He graduated from Moreno Valley High School in 1974 and attended college at the University of California, Riverside, graduating in 1979, and medical school at the University of California, Los Angeles, receiving a Ph.D. in 1985 and M.D. in 1987. He served in the United States Marine Corps Reserve from 1979 to 1985, and moved to Salem, Oregon in 1994, where he currently works as an oncologist and hematologist. Pierce is also a clinical assistant professor of medicine at Oregon Health & Science University and College of Osteopathic Medicine of the Pacific, Northwest.
