Pire became a monk, taking his final vows in 1932. He then studied theology and the social sciences at the Dominican University in Rome, receiving his doctorate in theology in 1934, and returned to the monastery in Huy, Belgium. During the second world war, Pire served as chaplain for the Belgian resistance and actively participated, helping to smuggle Allied pilots out of the country, for instance. He received several medals for this service after the war.
In 1949, he began studying issues relating to postwar refugees and wrote a book, Du Rhin au Danube avec 60,000 D. P. about them, and founded an organisation to help them. The organisation organised sponsorships of refugee families, and during the 1950's built a sequence of villages in Austria and Germany to help house many refugees.
After winning the Peace Prize, Pire also helped to set up a "Peace University" and commenced projects to assist the rural poor in Bangladesh and India.
He died from complications from surgery.