Named to lead the Brooklyn Diocese Aug. 1, 2003 , after four years as the Bishop of the Diocese of Camden, Bishop DiMarzio was installed in his new See at a ceremony and Mass both solemn and joyous at Our Lady of Perpetual Help Basilica in Brooklyn Oct. 3, 2003.    
                           
With strong ministerial and family ties to New Jersey, the Newark-born prelate began his ministry among migrants in l976---six years after his ordination as a priest of the Archdiocese of Newark on May 30, 1970---as the archdiocese's refugee resettlement director for nine years, during which time he also served a two-year term as director of the Office of Migration of Newark's Catholic Community Services.
     
Father DiMarzio moved to Washington in l985, when he was appointed executive director of Migration and Refugee Services for the U.S. Catholic Conference, and served there for six years. A year after arriving in Washington, he was named a Prelate of Honor by Pope John Paul II.

Upon Msgr. DiMarzio's return to his home archdiocese in 1991, Archbishop Theodore E. McCarrick appointed him to be the associate executive director of Catholic Community Services and a year later he advanced to executive director, a position he held for five years. A certified social worker with a doctorate in social work research and policy from Rutgers University, he also held the title of Vicar for Human Services.

In l996, Pope John Paul II elevated him to the rank of Auxiliary Bishop, and from l998 till 2001 he chaired the Migration Committee of the U.S. Conference of Catholic Bishops. Since then he has served as chairman of the Catholic Legal Immigration Network. Inc., and in 2000 he was appointed a member of the Pontifical Council for the Pastoral Care of Migrants and Itinerant People.

Because of his wide-ranging knowledge and experience in matters affecting migrants and immigrants, Bishop DiMarzio has testified frequently before committees of the U.S. House of Representatives.

Appointed the sixth Bishop of Camden June 8, 1999, he undertook several initiatives, including establishing an Office of Ethnic Ministries, an Office of Black Catholic Ministry and an Office of Hispanic Ministry. He also created an apostolate to the Haitian community and founded two missions to serve the Korean and Vietnamese communities.

One of Bishop DiMarzio's first acts after his installation as Bishop of Brooklyn was to speak at the Immigrant Workers Freedom Ride Rally at Flushing Meadows Park. In November he spoke before Brooklyn's Muslim community at a Ramadan celebration and attended the Fifth World Congress of the Pontifical Council for the Pastoral Care of Migrants and Itinerant People in Rome.

Shortly after becoming the Bishop of Brooklyn, Bishop DiMarzio was invited to be a member of the Global Commission on International Migration, formed by the Secretary General of the United Nations and a number of governments.  It began its work in December, 2003 and concluded Dec. 31, 2005 after completing a report, entitled "Migration in an interconnected world; New directions for action."The Bishop was the only U.S. citizen on the 19-member commission.

Bishop DiMarzio has issued three pastoral letters addressed to the parishioners of the Diocese of Brooklyn.  The first, "The New Evangelization in Brooklyn and Queens," was presented in October, 2004.  The following October he wrote his second pastoral, entitled "The Family: The Hope of the New Evangelization."

In October, 2007, the Bishop issued his third pastoral letter: "Do Not Be Afraid - A Pastoral Vision for the New Evangelization."

Since November, 2004, Bishop DiMarzio has chaired the Domestic Policy Committee of the U.S. Conference of Catholic Bishops.  He is also a member of the Bishops' Migration Committee, treasurer of the board of directors of Catholic Relief Services, and a member of the Bishops' Task Force on Catholic Bishops and Politicians.

Bishop DiMarzio's column of reflections on issues affecting the faithful, entitled "Put Out Into the Deep," appears weekly in the diocesan newspaper, The Tablet.