Cornelio Fabro is born in Flumignano (Udine) on the 24th of August, 1911 (baptized at Saints Peter and Paul the Apostles Parish, with the name of Cornelio Remigio on August 27, 1911, by the priest, Aristide Luccardi, OFM Cap.). In the aforementioned Parish, he receives First Communion in 1920 and Confirmation (November 28, 1920). He is the third of four children (all native of Flumignano): Antonio, Secondo, Cornelio Remigio, and Alma Teresina.

An infancy so tried by serious illnesses conditions the scholastic approach quite a bit, but only the approach, as we can assert, in comparison with his progressive cultural recognition. Fabro did not attend the classes of first, second, or fifth grade regularly. He attended only third grade at Flumignano and fourth grade at Talmassons (near his birthplace).

Fabro recounts his priestly vocation:

"My religious and priestly vocation did not have a precise beginning. I was little—that is, since I began to walk and attend Church and follow the ceremonies, I felt a great impulse for holy things. I would repeat the sermons and the Pastor’s teachings at home—at the time he was curate, that is, chaplain; the parish was Talmassons—and I would often celebrate Holy Mass (in my own way!) Mom would let it go. At the age of ten, I spoke for the first time with the pastor, Don Vasinis, who was really fond of me, but didn’t influence my decision in any way. Mom, however, (as I have already mentioned) arranged a good talking-to for me, putting me before the great duties of the Priest. (It was the spring of 1922 and we were in the kitchen.) I got the message well enough, but, as often happens with me, I stayed with my decision. Several weeks later, the Stigmatine, Father Edoardo Castellani, a priestly figure very popular in Friuli, came to the village, again to preach. He spied me immediately and arranged with Mom to send me to the student residence of the Stigmatines at Most Holy Trinity in Verona."