Some 300,000 believers - pilgrims from Croatia, Bosnia and Herzegovina, Slovenia and some other European countries - are participating in the celebration of the Eucharist with 1,100 priests in front of the altar.
Before the start of the mass, Zagreb Archbishop Cardinal Josip Bozanic said he was confident that the Holy Father's presence and his words would be an encouragement to all families and also further promote the family as the most sacred institution of a healthy society.
He said that pastoral efforts and care were being focused on the family, in an attempt to deal with challenges which put to the test the values of the family and the dignity of life.
Today's event is the crown of those efforts, giving fresh impetus to the commitment to the family, the Croatian dignitary said.
Today's holy day is imbuing the hearts of people from the entire Croatia with reverence and love towards the Pope, he said, adding that Croatian bishops, clergy, the faithful as well as cardinals, priests and pilgrims from other countries, notably from Bosnia and Herzegovina, were here together in Christ.
He recalled the celebration of the Eucharist at the same place in 1994 when Pope John Paul II paid the first pontifical visit to Croatia.
Cardinal Bozanic once again thanked Pope Benedict for everything he was doing for Croatia and for his commitment to the Croatian people.