Cardinal Konrad Krajewski broke into an abandoned government building where 450 homeless people are living.
Authorities cut off power and water to the building last week because of an unpaid bill reported to be more than $300,000.
Krajewski ignored the possible legal consequences when he broke the police seal on the building, went underground, and flipped a switch to turn the lights back on in the darkened building.
A nun who works with the homeless told Italian radio and television that when workers went to the building to cut off the power again, they found a note from the cardinal asking them to leave it on.
Krajewski called his act “a gesture of desperation.”