Pope Francis chose to change clothes in a fast-food restaurant in the Bolivian city of Santa Cruz before leading an open-air Mass before an audience of hundreds of thousands.
The famously unpretentious Pope used his address to encourage Bolivian Catholics to reject consumerism.
He told them the economic system excluded people and created barriers.
The Pope will now travel to Paraguay, the third and final country on his tour of South America.
On Thursday Pope Francis rode through the streets of Santa Cruz for about an hour.
The Burger King restaurant had been booked by the Pope’s organisers and curtained off in advance so he could change into his religious vestments before the Mass.
It reopened later in the day for business but with the altar and throne used in the Mass still inside.
During his sermon he denounced what he said was a “mentality in which everything has a price, everything can be bought (…) making room only for a select few”.
Later in a long speech to civic leaders, Pope Francis apologised for the actions of the Catholic Church against indigenous peoples during the conquest and colonisation of the Americas.
He said he humbly begged for forgiveness for the crimes that were committed.