At eight years old, John heard a visiting priest speak of adventures that were waiting in the age of 1503 with new worlds being opened up. That very night he ran away from home to travel with the priest and never saw his parents again. They begged their way from village to village until John fell sick. The man who nursed him back to health, the manager of a large estate, adopted John. John worked as a shepherd in the mountains until he was 27.

As a shepherd he had plenty of time to contemplate what God might want of his life. When he decided at 38 that he should go to Africa to ransom Christian captives, he quit immediately and set off for the port of Gibraltar. He was on the dock waiting for his ship when he saw a family obviously upset and grieving. When he discovered they were a noble family being exiled to Africa after political intrigues, he abandoned his original plan and volunteered to be their servant. The family fell sick when they reached their exile and John kept them alive not only by nursing them but by earning money to feed them. John did go back home but only after he learned that his newly adopted family had received pardons.

In Spain he spent his days unloading ship cargoes and his nights visiting churches and reading spiritual books. Reading gave him so much pleasure that he decided that he should share this joy with others. He quit his job and became a book peddler, traveling from town to town selling religious books and holy cards. A vision at age 41 brought him to Granada where he sold books from a little shop. (For this reason he is patron saint of booksellers and printers.)
John of God is patron saint of booksellers, printers, heart patients, hospitals, nurses, the sick, and firefighters and is considered the founder of the Brothers Hospitallers.