"There are climbers in the Church. There are a lot of them!" the pope said in a homily during one of the morning masses he holds in the Vatican residence where he has stayed ever since being elected last year.
"People who follow Jesus for money, try to profit from the parish, the diocese, the Christian community, the hospital, the college," he said.
"We have known a lot of good Catholics, good Christians... And then we discover that they have been carrying out somewhat shady dealings. They were real profiteers and they made a lot of money!" he said.
Francis has said he wants a "poor Church for the poor" and has begun an overhaul of the scandal-hit Vatican bureaucracy and bank, the Institute for Religious Works.
Two former directors of the Vatican bank are facing trial in Italy for money laundering, and a former top Vatican accountant is a defendant in a separate trial for trying to smuggle money illegally through the bank.