Munonye was educated at Christ the King College in Onitsha (1943–48) and attended the University of Ibadan, graduating in 1952. He worked for the Nigerian Ministry of Education until 1977, when he left to teach and devote more time to writing.

Munonye's first novel, The Only Son (1966), describes the separation of a mother from her son because of religious differences. Obi (1969), a sequel to The Only Son, broadens the theme to an extended family and the clash between African traditions and European beliefs. In both books the family emerges as a source of strength in times of turmoil. Munonye's later novels include Oil Man of Obange (1971) and A Wreath for the Maidens (1973). His novel A Dancer of Fortune (1974) is a satire of modern Nigerian business. Munonye returned to the family of his first two novels in Bridge to a Wedding (1978). Thereafter he published little.