Actually, there were four popes during Pier Giorgio's short lifetime.

The first, Pope Leo XIII, took office in 1878 and was pope at the time of Pier Giorgio's birth in 1901. The encyclical, Rerum Novarum, published by Pope Leo XIII in 1891, had a profound effect on Pier Giorgio. It was the first of the great social encyclicals addressing the rights and duties of capital and labor and recognizing the human dignity of the worker. Blessed Pier Giorgio's efforts in support of the working class have been well documented. Even his career choice of mining engineering stemmed from his desire to work among and serve the poorest of the poor.

When Pier Giorgio was just two years old, Pope Saint Pius X took office. One of the changes implemented during the pontificate of Pius X was most significant for Pier Giorgio. Pope Pius X advised everyone to receive Holy Communion daily, if possible, and he recommended that children should make their First Holy Communion not long after reaching the age of reason (around seven years of old.) Until then, it had been the practice to wait until one had been confirmed, around the age of 12 or older. This enabled the daily reception of the Eucharist to become a part of Pier Giorgio's sacramental life from a very early age.

Pope Benedict XV succeeded Pope Pius X in 1914. He also had an influence on Pier Giorgio in a special way. In 1922, Pier Giorgio organized a raffle to raise funds for the work of his Cesare Balbo Club. The Pope donated an item to the raffle which Pier Giorgio ended up winning. He wrote about it in a letter to his mother and sister on February 21st of that year: "I had the immense good fortune of winning the gift donated by His Holiness Benedict XV..." The gift was a picture of the “Madonna della Seggiola” in a case with doors that opened, and the Pope had sent it to the raffle a few days before his death in January. Pier Giorgio treasured it his whole life. As he lay dying, he wanted this picture to be nearby on the improvised altar in his bedroom in Turin. Today, the picture can still be seen in his bedroom which is now located in the family villa in Pollone.

In 1922, Pope Pius XI took office. Later that year, he inaugurated the Catholic Action movement. The goal of this movement was to involve lay people in the effort of actively spreading Catholic values and political ideas throughout society. Blessed Pier Giorgio was a dedicated member of Catholic Action. In his letters, he often cited the efforts of Pope Pius XI to promote peace.

Each of the four popes during Blessed Pier Giorgio's lifetime played some part in his spiritual formation. In turn, Pier Giorgio had a great love for the papacy. In April 1922, he wrote the following to his friend, Mario Bergonzi, who lived in Rome: