The pontiff's allowing Catholic bishops in individual countries to decide what day it should be on, rather than putting it on one set day for the whole Church, because some already host days of prayer for abuse survivors.
His approval means a day of prayer for victims will become much more widespread across the Church.
It was proposed by the Pontifical Commission for the Protection of Minors, which has also developed draft new safeguarding guidelines for the Vatican to be reviewed by the Pope.
The Commission is also launching its own website where it will regularly post updates of its work, in a bid to boost accountability.
It said: "The Commission believes that prayer is one part of the healing process for survivors and the community of believers.
"Public prayer is also an important way of consciousness raising in the Church."
