The pontiff urged his fellow clergymen to "use your brains more" during a closed-door meeting with the clergy of the Diocese of Rome last month.
The details of the meeting, in which the Pope took questions from priests, were unsealed the following day and reported by Vatican News.
During the meeting, the head of the Catholic Church told listeners that giving a "homily is to share faith" and argued that AI "will never be able to share faith".
Pope Leo warned: "Like all the muscles in the body, if we do not use them, if we do not move them, they die.
"The brain needs to be used, so our intelligence must also be exercised a little so as not to lose this capacity."
The 70-year-old pontiff also spoke out against social media as he asked members of the clergy to be wary of chasing "likes" and "followers" through an "illusion on the internet, on TikTok".
This isn't the first time that the Pope has spoken out against AI, as he warned men not to form emotional attachments to chatbot "girlfriends" earlier this year.
Speaking on the World Day of Social Communications in January, the pontiff said it is becoming "increasingly difficult to determine whether we are interacting with other human beings or with bots" in the modern digital world.
He urged Catholics to protect authentic human connection, stressing the importance of "preserving human voices and faces" in an era dominated by artificial intelligence.
The Pope said: "Faces and voices are sacred. Digital technology threatens to alter radically some of the fundamental pillars of human civilisation that at times are taken for granted."
Pope Leo expressed particular concern about AI chatbots designed to simulate romance or emotional intimacy.
He said: "Because chatbots are excessively ‘affectionate', as well as always present and accessible, they can become hidden architects of our emotional states and so invade and occupy our sphere of intimacy.
"Technology that exploits our need for relationships can lead not only to painful consequences in the lives of individuals, but also to damage in the social, cultural and political fabric of society."
