Most Reverend Thomas J. Walsh, S.T.D., J.C.D., formerly Bishop of the Trenton Diocese was appointed Fifth Bishop of Newark on March 2, 1928. Bishop Walsh chose to use the new Cathedral for worship for the first time. It was decided that his installation would take place on May 1, 1928 in the unfinished Cathedral. The Diocese was divided again in 1937 to form the Paterson Diocese. This new Diocese served the counties of Morris, Sussex and Passaic. The Newark Diocese continued to serve the counties of Essex, Bergen, Hudson and Union. In that same year the Newark Diocese was elevated to the rank of Archdiocese and Bishop Walsh was appointed Archbishop on December 10, 1937. He was installed as Archbishop on April 27, 1938 in the Cathedral.
Walsh had studied at St. Bonaventure College in New York and was ordained on January 27, 1900. He went to Rome in 1907 to study canon law and six months later he received another degree, Doctor of Sacred Theology.
In continuation of the educational mission within the diocese Walsh stated, "I'd rather lay the cornerstone of one Catholic school than lay the cornerstones of 10 Catholic Churches." He raised $2 million dollars in 25 days to build the Immaculate Conception Seminary in 1936, (today that would be $1.2 billion +). He pushed for Seton Hall Prep and Seton Hall College to receive state accreditation in 1931 and 1932 respectively. He laid the cornerstone for the auditorium/gymnasium; he would later be the #1 fan of the basketball team. In 1948 he officially opened the college radio station, WSOU. The following year he launched plans for the college to earn University status.
Walsh oversaw the launch of the Diocesan newspaper, The Advocate, which first appeared on December 30, 1951. Walsh said of the newspaper, "I want it to be a real newspaper, not just the goings and comings of the Archbishop." Archbishop Walsh passed away on June 6, 1952 and was buried in the Cathedral crypt where Bishop O'Connor had previously been laid to rest.