Nick Smith is back, now that the final step in the National-led Government's cabinet reshuffle is complete.
The new ministers were sworn in by the Governor-General this morning.
A visibly moved Dr Smith returned to Cabinet as housing and conservation minister at the ceremony at Government House.
He stepped down from the Environment and ACC portfolios last year after he was found to have written a testimonial supporting a friend's ACC claim.
Prime Minister John Key said Cabinet had missed Dr Smith's intellect and ``prodigious work-rate''.
Auckland Central MP Nikki Kaye was sworn in as minister for food safety, civil defence and youth affairs.
Dunedin-based list MP and former chief whip Michael Woodhouse was given responsibility for immigration and veterans' affairs.
Mr Key told them: "Very few things or events will bring so much pride and joy and excitement to you as the day you receive your first warrant.
"You've got here because you've demonstrated in your time in Parliament that you have good judgement, that you're prepared to work hard, and that you have the best interests of New Zealanders at heart.''
Governor General Sir Jerry Mateparae acknowledged departing ministers Kate Wilkinson - who held the Labour and Conservation portfolios - and Phil Heatley, who held the energy and resources and housing roles.
Tauranga MP Simon Bridges took on the energy and labour portfolios.
Mr Key said: "The hard work begins at 3.01pm when we elect a new Speaker.''
Former Minister for Primary Industries David Carter was expected to be elected as Speaker this afternoon after the departure of Lockwood Smith.