[4] Her father was a Samoan-Tongan migrant freezing worker, who migrated to New Zealand without being able to speak English, and "staunch unionist" and her mother was a Pākehā from a conservative farming family.

[13] On 19 March 2010, Sepuloni was selected as the Labour candidate for the Waitakere electorate in the 2011 general election, facing incumbent National MP and Cabinet minister Paula Bennett.

[17] Not long after leaving Parliament Sepuloni travelled to Egypt to participate as a short-term observer on the NDI International Election Mission.

Prior to being reelected, Sepuloni was employed as the chief executive of Vaka Tautua, an Auckland-based Pacific disability, mental health, and social services provider.

[24] On 28 April 2018, Sepuloni issued a statement criticising Work and Income for turning away a homeless woman who was trying to apply for a benefit after being discharged from hospital.

[25] As social development minister, Sepuloni likened her Government's approach to welfare reform to "trying to turn a jumbo jet in mid-air.

[27][28]During the 2020 general election held on 17 October, Sepuloni was re-elected in Kelston by a final margin of 15,660 votes, retaining the seat for Labour.

[29] In early November, she retained her previous ministerial portfolios for social development, disability issues, and ACC, while also becoming the minister for employment and arts, culture and heritage.

[36] In early November 2023, along with the National Party's foreign affairs spokesperson Gerry Brownlee, she represented New Zealand at the 2023 Pacific Islands Forum.

[38] In late November 2023, she became Deputy Leader of the Opposition and spokesperson for social development, Pacific Peoples, Auckland issues, and child poverty reduction in the Shadow Cabinet of Chris Hipkins.