She is a Member of Parliament and co-leader of Te Pāti Māori alongside Rawiri Waititi,[3][4] and is the chief executive of the Ngāti Ruanui iwi.

[22][23] In 2011, she joined a 10-member independent panel set up by the Government to identify ways to raise the rate of return on Māori-owned assets, and grow Māori contribution to New Zealand's economy.

"[34] Writing in December 2020, journalist Marc Daalder said, "Waititi and Ngarewa-Packer have already garnered a reputation for – depending on who you ask – rabble-rousing, troublemaking or standing up for their rights.

"[35] In a 2021 interview, Ngarewa-Packer said her goals included helping whānau access safe housing, along with achieving better incomes and health outcomes.

She and a team of volunteers spearheaded a mobile programme to lift Covid vaccination rates in South Taranaki for "yaks and vax" sessions.

At one event Niel Packer, Debbie Ngarewa-Packer's husband, was punched in the face by a man angry at the vaccination program.

[52] In mid-December 2023, Ngarewa-Packer retained her position as Te Pāti Māori co-leader and joined Parliament's health select committee.

She also assumed the party's health, climate change, environment, energy & resources, Takatāpui, digital economy, Accident Compensation Corporation, immigration, Pacific Peoples, human rights, and technology spokesperson portfolios.

"[54] Te Pāti Māori also advocated the expulsion of the Israeli Ambassador Ran Yaakoby if Israel did not implement a ceasefire or open a humanitarian corridor in Gaza.

[55] In opposition, Ngarewa-Packer disagreed with the National-led coalition government's repeal of the Smokefree Environments and Regulated Products (Smoked Tobacco) Amendment Act 2022.

After Chief Ombudsman Judge Peter Boshier rebuked the Associate Health Minister Casey Costello withholding official Information Act requests for documents relating to the Government's tobacco policies, she called for a full inquiry into the Government's tobacco reform actions, alleging that Costello withheld information when pushing through the Smokefree repeal legislation under urgency.

She along with Hana-Rawhiti Maipi-Clarke, Rawiri Waititi and Labour MP Peeni Henare performed an impromptu haka (ka mate) which disrupted the bill's first reading.

On 10 December 2024, House Speaker Gerry Brownlee referred Ngarewa-Packer and her three colleagues to the Privileges Committee for disrupting parliamentary proceedings.

[57] In early December 2024, Ngarewa-Packer advocated capital gains taxation, claiming that the Government could raise NZ$200 billion from such a tax over six years.

She based her figures on remarks made by journalist Bernard Hickey during a debate with ACT leader David Seymour.

[19] She is a descendant of Tutange Waionui of Ngāti Ruanui, who fought alongside Tītokowaru during the New Zealand Wars and claimed credit for killing Prussian mercenary Gustavus von Tempsky.

[5][61] In mid-December 2024, Ngarewa-Packer was allegedly verbally abused and intimidated by a middle-aged European (Pākehā) man while visiting a Whanganui petrol station.

In response, Te Pāti Māori denounced the incident as a "hate crime," filed a Police complaint and sought extra security and protection for its MPs from the Speaker of the New Zealand House of Representatives and Parliamentary Services.