RBNZ governor Adrian Orr said he was delighted to have Silk's leadership and experience in such an important role at Te Pūtea Matua.
"Silk has a wealth of leadership experience in banking. She has been a senior leader across retail and wholesale banking, wealth management, financial market infrastructure and payment systems," Orr said.
"These are all areas where the RBNZ has significant projects underway."
Orr said Silk was also experienced in climate change and risk management, including being co-chair of the Sustainable Finance Forum.
"She is a respected leader in the banking sector."
Silk will take up the role at the Reserve Bank in coming months, with a start date to be confirmed in due course.
She will also sit on the Reserve Bank's monetary policy committee which decides what will happen to the official cash rate.
The RBNZ has made three other assistant governor appointments in the last month.
Late last year it faced criticism over high turnover in its senior staff with a number of departures.
Of its 26 tier two or three staff, 10 left in the six months prior to Christmas or were leaving in the next six months.
Orr was forced to defend workplace relations at the central bank and his leadership style when he was grilled in Parliament by Opposition MPs before the Finance and Expenditure Committee following the departures of four long-serving staff.
Reserve Bank chairman Neil Quigley expressed confidence in Orr's handling of the bank's restructure when approached by the Herald, calling staff turnover "unfortunate but normal".
"The Reserve Bank is going through a change process designed to provide it with the capability it needs for its current and anticipated future operations. I have complete confidence in the Governor's leadership of this change process," Quigley, the vice-chancellor of University of Waikato, said.
