Prime Minister Jacinda Ardern said reaching the milestone was "significant and heartening".
"Our Parliament will always be better when the diversity of voices in New Zealand are heard in our law making and government.
"The Labour Party in particular has been deeply committed to having equality of representation within our own caucus and we are really excited to welcome Soraya to our team."
Peke-Mason will also be the first MP sworn in by the new Speaker, her cousin Te Tai Hauāuru MP Adrian Rurawhe, and the first new MP pledging allegiance to the new King, Charles III.
Representing the Rangitīkei electorate and supported by kaumātua and whānau from the river and mountain tribes and Rangitīkei, she will be sworn in at 2pm, in te reo Māori, and will give her maiden speech at 5.45pm.
"It is an honour and a privilege to be going to Parliament to represent our rohe," Peke-Mason said.
"Over the last one or two decades, my work has taken me across the Whanganui, the Ruapehu and the Rangitīkei districts.
"I'm excited and proud to be able to represent our rohe, and for Te Awa Tupua, for Rangitīkei, for all of us to have another strong voice at a table that makes really important and hard decisions on behalf of Aotearoa."
It's two years since Peke-Mason missed out at the 2020 election. Her elevation to Parliament was announced in June after news that Kris Faafoi would leave politics and Trevor Mallard would move on to a diplomatic posting.
Peke-Mason, who lives at Rātana south of Whanganui, was Rangitīkei's first wahine Māori councillor for 12 years until 2019 when she unsuccessfully ran for Horizons Regional Council.
In 2020, she stood in the general election in Rangitīkei against incumbent Ian McKelvie and was ranked No 60 on the Labour list.
"After the results of the last election, there was a possibility that I could enter Parliament but you just get on with it. You leave that there to the side and you just get on with your mahi at home."
She was appointed to the Whanganui District Health Board and to its Hauora ā Iwi Relationship Board. She also helped lead the Whanganui Māori Regional Tourism board, was a member of Rangitīkei District Council's Te Roopu Ahi Kā and held a number of iwi Māori and Māori trust governance roles.
"I've had plenty of time to be able to exit the work that I've been doing in the rohe, to tidy up those loose ends, to finish up projects properly, look at replacements, and work with Māori authorities that I've done work for to ensure there's an appropriate exit process so that they're not left in the lurch, and I've also been able to exit some of the boards I've been on.
"I've been lucky to have the time to do that. Not every MP gets that time."
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