According to Savannah Morning News the Pope is due to stop off in Cuba at the end of September as part of his USA tour.
After leaving the Vatican it was reported that Castro was full of praise for the Pope and said he "is a Jesuit, and I, in some way, am too."
At a news conference at the office of the Italian Prime Minister, he said that "when the pope goes to Cuba in September, I promise to go to all his Masses, and with satisfaction."
"I read all the speeches of the pope, his commentaries, and if the pope continues this way, I will go back to praying and go back to the church, and I'm not joking."
This is an unexpected statement from the communist leader, whose crackdown on religion in the country has previously invited criticism from the Vatican.
Castro said: "I am from the Cuban Communist Party, that doesn't allow (religious) believers, but now we are allowing it, it's an important step."
He added that he had been delighted with the Pope and said he was: "very impressed by his wisdom, his modesty, and all his virtues that we know he has."
Castro had already publicly thanked the Holy Father for bringing the USA and Cuba closer again.