The pontiff missed a step and fell to the ground as he was coming to an open-air altar to celebrate Mass at Poland's holiest shrine of Jasna Gora.
Priests raced around to help 79-year-old back to his feet and sort his robe.
The Mass went ahead as planned and the pope delivered a sermon before tens of thousands of faithful Catholics.
The crowd gathered at the foot of the Jasna Gora monastery in the southern city of Czestochowa.
Pope Francis is in Poland to celebrate World Youth Day, the biggest celebration of its kind with millions of Catholics in attendance from all over the world.
It is the Argentinian pontiff's first journey to Eastern Europe.
