He was raised in the Yeadon section of Philadelphia, along with his older sister, Joan, and three younger brothers, Joseph, James, and John.

[citation needed] Cullen was sent by Archbishop Krol to study at the University of Pennsylvania, earning his Master of Social Work degree in 1970.

[4] Cullen was raised by the Vatican to the rank of honorary prelate in April 1982,[1] and served as director of Catholic Social Services from 1983 to 1988.

He received his episcopal consecration on April 14, 1994, from Cardinal Anthony Bevilacqua, with Archbishops John Foley and Francis Schulte serving as co-consecrators.

[1] In January 2004, Cullen stopped allowing the celebration of mass and other sacraments at The National Centre for Padre Pio in Barto, Pennsylvania, located in the diocese.

The report showed that Cullen, as bishop of Allentown, instructed his vicar general, then Monsignor Alfred Schlert, to act as an "enabler" when handling abuse allegations.

The grand jury report involved six Pennsylvania dioceses, and it stated that "we believe that the real number — of children whose records were lost, or who were afraid ever to come forward — is in the thousands.