The son of a Baptist minister, Medearis was born in Fayette, Missouri and later moved to Miami, Oklahoma. He studied with regionalists Thomas Hart Benton and John DeMartelly at the Kansas City Art Institute. Medearis remained friends with Benton, and often swapped technical secrets with Tom.

During World War II, Medearis supported the war effort by drafting the finest topographic maps and charts for field artillery and naval air force units. In his professional years as a business executive, Medearis devoted little time to his art, but returned to painting and lithography in 1960s and created rural scenes in delicate tones reminiscent of his earlier works.