A video wall and sound system have been installed in front of the Zagreb Cathedral for this purpose.
Apart from Croatians, also young people from Bosnia and Herzegovina, Austria, the Netherlands, Germany, Serbia and Macedonia will attend this event.
Some 10,000 participants in the Prayer Vigil are arriving at the Zagreb Fair facilities, after which they will walk to the main square.
The official programme of the Prayer Vigil is scheduled to start after 1900 hrs Saturday.
The pope will join the gathering after his meeting with prominent figures from the Croatian political, social and cultural life in the Croatian National Theatre.