C. A. DeFehr was a successful businessman in Russia and in Canada who was extensively involved in the affairs of the Mennonite constituency. He was born in Einlage, Chortitza to Abraham A. DeFehr and Helena Peters. He was baptized and joined the Mennonite Brethren Church in Petrovka in 1901. He was married to Elizabeth Dyck in1903, in Millerovo, South Russia. Cornelius and Elizabeth had six children, with four reaching adulthood. DeFehr's first business venture was a partnership in a manufacturing industry in Millerovo in 1904. The family moved to Manitoba and by 1926, had established an import business in Winnipeg which became a prosperous family enterprise with branches in Edmonton, Regina, and Saskatoon.
C.A. DeFehr was very active in matters pertaining to the Mennonite people. In Russia he was appointed as one of the chief administrators of the massive relief effort during the famine. In Canada he was active in a large number of Mennonite Brethren committees, including the Winnipeg City Mission, the Mary-Martha Girls' Home, Mennonite Brethren Collegiate Institute, and Christian Press. DeFehr was also very active with the Mennonite Central Relief Committee of Western Canada, serving as secretary-treasurer for many years. He directed the resettlement of Mennonite refugees in Paraguay after World War II.