The acts were already crimes under church law, CNN said, but are now specifically outlawed within the Vatican, which is home to hundreds of people.
The measure also covers child prostitution, and the creation or possession of child pornography.
The new law is part of an update to the Vatican's legal system, which began under Pope Benedict.
Pope Francis issued the law as a moto proprio, meaning the measure was his own initiative.
Celebrity Families of 2014 [PHOTOS]