Maori Party MPs will walk on to the marae at Ratana Pa, near Wanganui on Friday afternoon with Prime Minister John Key and 27 National MPs.
It will be the first time both parties have been welcomed to the annual celebrations together, a sign of closer relations between them.
Mr Key says his address will focus on the Government's commitment to achieve a better future for Maori.
The Labour Party, which has strong links to the Ratana movement, will be welcomed onto the marae earlier, at about 11am.
The Ratana celebrations are often described as the beginning of the political year.
But Maori Party co-leader Tariana Turia says it's really a time for the followers of the Prophet Ratana.
The celebrations culminate on Sunday, which will be the 136th anniversary of Ratana's birth.