James Hahn was born on July 4, 1937 in Chicago, Illinois to William Patrick Hahn and Adelaide Irene Olden Hahn. He had one sister, Patricia Welch of Dover, Delaware. He was a student at Providence College where he got to know the friars. He entered the novitiate in 1957, at St. Rose of Lima Priory in Springfield, Kentucky as a son of the Province of Saint Joseph and was given the name Cornelius. He made his first profession on August 16, 1958 and obtained his B.A. degree in Philosophy at St. Stephen College in Dover, MA. He did his theolog studies at the Pontifical Faculty of the Immaculate Conception in Washington, DC. He was ordained a priest on June 11, 1964 at Saint Dominic Church in Washington, DC.

In 1970, he received a Master's degree in speech from the Catholic University of America. He served in numerous ministries, including provincial secretary for the Eastern Dominican Province, parochial vicar, speech therapist, instructor in communications, theology, and homiletics, Director of the Shrine of St. Jude and for many years as an itinerant preacher.

In 1980, his petition to the Master of the Order to transfiliate to the Province of Saint Albert the Great, was granted. He served as Prior of St. Pius V Priory in Chicago, Blessed Sacrament Priory in Madison and St. Dominic Priory in Denver. It was during his term as Prior of Denver he resigned because of advanced Parkinson disease and moved to the Provincial Health Care Center at Saint Pius V Priory in Chicago. After a sudden decline in his health, he died on November 8, 2008. The Office of the Dead and the Mass of Christian Burial were celebrated at St. Pius V Church. He was interred in the Dominican plot at All Saints Cemetery in Des Plaines, Illinois.