He made his profession as a member of the Congregation of the Passion on July 24, 1887, taking the religious name of Paul Joseph.
[2] Nussbaum was ordained to the priesthood for the Congregation of the Passion in Rio De Janeiro by Archbishop João Fernando Santiago Esberard on May 20, 1894.
Nussbaum returned to the United States in 1904 to first serve as a curate in a parish in West Hoboken, New Jersey, then in Dunkirk, New York.
[3] He received his episcopal consecration on May 20, 1913, from Archbishop Giovanni Bonzano, with Bishops John O'Connor and Charles McDonnell serving as co-consecrators, in West Hoboken.
[3][1] As bishop, Nussbaum founded St. Ann's Society for married women, and promoted the Forty Hours' Devotion and daily communion.