Born to Jewish parents. From his early youth he loved to write, keeping diaries and endlessly corresponding. Attended the University of Vienna. Married to Elsa Reiss in 1912. Graduated as a physician in 1914. Joined the Catholic Church on 23 December 1914. Father of three.
After the war he settled in Pola, Italy (in modern Croatia) and set up a medical practice. He changed his last name to Labor to downplay his Jewish origins, and to show his sympathies with the Socialist movement. Helped the working poor of his city, became more involved in his Catholic faith, and in its application to the social issues of his city. Published over 200 pieces on the topics in local newspapers and magazines through the 1930’s. Worked with the Saint Vincent de Paul Society and Catholic Action in his area. Founded a Catholic Center to teach doctrine and encourage devotion to the Eucharist.
A widower in 1934, Marcello began studying for the priesthood. Ordained in the diocese of Trieste, Italy on 21 September 1940. Rector of the seminary of Koper and Trieste. Parish priest. Spiritual director of the Theological Seminary of Central Gorizia. Pastor of the Cathedral of San Giusto. Noted preacher and spiritual director.
From 1943 to 1945 Father Marcello was exiled by the Fascists for the dual offenses of being both Jewish in origin and a Catholic priest; both were groups heavily persecuted by the Axis powers during World War II. Imprisoned in 1947 by the anti–Christian Communists led by Tito. Having supported Socialism in his youth, he was persecuted both by the Fascist and Communist versions, and came to understand the only truth he had found was in the Church.
- 29 September 1954 in Trieste, Italy of a heart attack
- buried at the Church of Saint Anthony the Wonder Worker in Trieste
- his grave marker reads Marcello Labor, Former Parish Priest of San Giusto
- “Venerable Marcello Labor“. CatholicSaints.Info. 11 June 2015. Web. 27 October 2016. <>