Passionate about fantasy and illustration, Mayo dropped out of pharmacy studies and pursued studies in fine art. He graduated from the National School of Fine Arts in Lima and quickly established a career illustrating advertisements for television shows such as Lawman, Cheyenne, Gunsmoke, Batman and Ivanhoe.

Mayo left Peru after the military coup of October 1968. He moved to Mexico City and illustrated comics such as Fantomas, Sherlock Holmes and Tarzan. This caught the attention of Jim Warren who hired him in 1973 to illustrate Vampirella.

After Warren closed, Mayo worked for DC, Marvel, Valiant, Disney and other comics companies.