The Catholic leader, who heads the 1.2 billion-strong Church, made his comments in the homily of his morning Mass in his residence, a daily event where he speaks without prepared comments.
He told the story of a Catholic who asked a priest if even atheists could be redeemed by Jesus.
"Even them, everyone," the pope answered, according to Vatican Radio. "We all have the duty to do good," he said.
"Just do good and we'll find a meeting point," the pope said in a hypothetical conversation in which someone told a priest: "But I don't believe. I'm an atheist."
Pope Francis's comments are in marked contrast to his predecessor Benedict, who is reported to have left some non-Catholics feeling that he saw them as second-class believers.