The Act Party has signed a deal to work with National for another three years, but the agreement does not include a ministerial portfolio for new MP David Seymour.
Mr Seymour, 31, has been given the roles of Parliamentary Under Secretary to the Minister of Education and Parliamentary Under Secretary to the Minister of Regulatory Reform.
The roles were more junior than a minister or associate minister but were still executive positions and carried some responsibility.
National Party leader John Key made the announcement this afternoon as Act signed a confidence and supply agreement with the National-led government for the third consecutive term.
Mr Key said the two parties had worked constructively for six years and he looked forward to the relationship continuing with Act's new MP.
National agreed to work with Act on further developing and expanding the charter schools programme.
The programme, introduced in the two parties' 2011 confidence and supply agreement, has established nine privately-run schools so far.
The two parties also agreed to work on "reducing the regulatory burden" which "held New Zealand back", and to prioritise reform of the Resource Management Act.
In a press conference this afternoon, Mr Key said it was "highly likely" that Mr Seymour would be made a minister before the end of the term.
"There's no formal agreement or backroom deal that says he will become a minister at a certain point.
"But I would have thought as he assumed his responsibilities and gets used to the working of Parliament ... it will be relatively easy to convert that over because it would make no change to overall size of the executive."
Mr Key said the under secretary role was "an elegant fit" in the short-term because it allowed Mr Seymour to gain some experience.
Asked if he deserved the role, Mr Seymour said "the proof will be in the pudding" and in the work Act did on education, poverty and inequality.
Mr Seymour would have some responsibilities for the charter schools programme, though his role did not allow him to act on the Education Minister's behalf.
Unlike a minister, an under secretary was not required to answer oral questions or written questions.
Mr Seymour would be entitled to a salary of $175,600, slightly more than the Parliamentary leader's base salary of $162,200.