While in high school, he also attended drawing classes at the British Council Art Club in Benin City.

During this time Onobrakpeya was inspired by the watercolour paintings of Emmanuel Erabor and a lecture given by Ben Enwonwu, art advisor to the Nigerian government.

[5] In October 1957, Onobrakpeya was admitted to the Nigerian College of Arts, Science and Technology, now the Ahmadu Bello University, Zaria.

Onobrakpeya has said that the college gave him technical skills, but the Zaria Arts Society shaped his perspectives as a professional artist.

[8] Onobrakpeya later attended a series of printmaking workshops in Ibadan, Oshogbo, Ife and Haystack Mountain School of Crafts, Maine, US.

The first segment is the Mythical Realism (1957–62), which represents paintings, and lino cut prints that depict folklore themes, and Northern landscapes (Zaria).

Works in this category include the paintings "Awhaire & the Bird", "Hunters Secret", and "A Tree in Northern Landscape", and the lino-cut prints "Zaria Indigo", "Two Faces", "Boli Woman" and "Awakening (Negritude)".

The Mask and the Cross (1967–78) series represents the period when the artist executed several Christian themes commissioned by the Church such as Nativity II (Iino engraving), The Last Days of Christ (plastocast), Obara Ishoshi (bronzed Iino relief) and Pope John Paul (metal foil), as well as the Plastography Period, a time when the artist developed a lot of ideas he started in Zaria in the late 1950s and early 1960s such as Travellers II, Songs of Life, and Rain & Cry at Otorogba.

These are pictures known as the Symbols of Ancestral Groves (1978–84) They depict historical figures, mostly royalty from the Benin Kingdom such as Oba Aka.

Since 1966, as an experimental artist, Onobrakpeya has discovered, innovated and perfected several techniques both in printmaking and relief sculpture that are uniquely Nigerian.

The used plastograph plates (like used lino blocks) have sculptural low relief effects which make them unique as art works.

A further development in plastocast relief is carving directly on abandoned or congealed plaster of Paris then applying resin on the cast and pulling out a positive.

Plastograph is a term given by Onobrakpeya to describe his deep etching technique that he innovated in 1967 through what he referred to as the Hydrochloric Acid Accident.

Additive Plastograph is another technique that involves making of print images on a sheet of sand paper, using glue as a drawing medium.

The thin foil is cut and placed on an engraved plate and then the embossed sheet is removed, turned over and filled with resin to stabilise the relief.

Ivorex is a new technique, recently developed by Onobrakpeya, which simulates optical effect of old ivory engraving on bone or elephant tusk.

The designs reflect the artist's knowledge of his Urhobo heritage, rich in symbols and the proverbs they elicit, as well as his appreciation of Chinese, Japanese, Ghanaian and Nigerian calligraphy.

Onobrakpeya invented and refined this script called Ibiebe from 1978 to 1986, when he revisited in his art, ideas linked with traditional religion, customs and history.

Published JANET L., STANLEY for the National Museum of African Art Branch Smithsonian Institution Libraries Washington, D.C. by Hans Zell London, 1993.