President Andrzej Dua and Prime Minister Beata Szydlo were among those who arrived for the service at the Temple of Divine Providence in Warsaw.
The Polish government first intended to construct the church in 1791, however, work has been delayed owing to centuries of war, occupation and communism.
Construction began twelves years after the fall of the Iron Curtain on 2nd May 2002 when a cornerstone blessed by Pope John Paul II was laid.
Nearly 100,000 people have contributed to the building of the Temple of Divine Providence which has reportedly cost £43million, with some work still to be completed.
The landmark's opening ceremony was held on Independence Day, an occasion which saw some nationalists take to the streets of Warsaw and carrying banners decorated with the far-right falange symbol.
In front of the Tomb of the Unknown Soldier in the Polish capital, President Duda led commemorations to mark 98 years since Poland regained its independence at the end of World War I.