He received his early education at Immaculate Heart of Mary School in Chester, and then attended St. Joseph's Preparatory College in Philadelphia.

[1] In 1894, at age 17, McNicholas entered the Order of Friars Preachers (more commonly known as the Dominicans) at St. Rose Priory in Springfield, Kentucky.

[2] The following year, the Dominicans sent him to Immaculate Conception College in Washington, D.C., where he served as regent of studies and professor of philosophy, theology, and canon law.

[1] He also served as the first editor of the Holy Name Journal and as pastor of St. Catherine of Siena Parish in Manhattan[1] He returned to Rome in 1917 to become an assistant to the master of the Order of Preachers and a professor of theology and canon law at the Pontifical University of St. Thomas Aquinas.

He received his episcopal consecration in Rome at the Santa Maria sopra Minerva on September 8, 1918, from Cardinal Tommaso Pio Boggiani, with Archbishop Bonaventura Cerretti and Bishop Hermann Esser serving as co-consecrators.

After the conversion of 70 African-Americans in the archdiocese to Catholicism, McNicholas said,"I earnestly ask all our colored citizens to consider the position of the Catholic Church, to study her teachings, to realize that her ceremonials, her processions, her music, are full of a profound meaning which, if understood, could not fail to stir the deepest emotion of the colored race.

[2] In 1948, Pope Pius XII wrote to McNicholas, as NCWC chair, urging the United States Government to accept European displaced persons as immigrants.

[8] The letter, later quoted in the 1952 Vatican document Exsul Familia on the rights of refugees, declares that such refugees sometimes have a right in natural law to be admitted to rich countries: "The sovereignty of the State, although it must be respected, cannot be exaggerated to the point that access to this land is, for inadequate or unjustified reasons, denied to needy and decent people from other nations, provided of course, that the public wealth, considered very carefully, does not forbid this.

"[8]On April 22, 1950, at age 72, John McNicholas died from a heart attack at his residence in the College Hill neighborhood of Cincinnati.

[13] The organization, which claimed at its high point a membership of 22,000,000, sought to influence decency standards in filmmaking and boycott films that it deemed offensive to Catholic teaching.