Auckland-based Salt Funds Management has been appointed as the external manager of AMP Capital's $690 million active New Zealand equities portfolios.
The AMP mandate will increase Salt's funds under management to more than $1 billion.
AMP announced in January that it would outsource its local active equities management operations to a third party.
That followed a string of staff departures from AMP, including former deputy head of equities John Phipps and portfolio manager Douglas Lau.
AMP said Salt's appointment followed a "comprehensive investment management search and evaluation process".
Salt was established in 2013 by former members of BT Funds Management, who went out on their own with a $650 million mandate from BT, which is owned by Australian banking giant Westpac.
The company, which specialises in Australasian equities and property investments, is owned by its staff, including managing directors Paul Harrison and Matthew Goodson.
Harrison said the new mandate would give Salt "critical mass".
"We're very happy with the position it puts us in," he said.
"AMP is a very good organisation to deal with and it's an iconic business here."
Harrison said Salt still had "headroom" to take on additional mandates.
The company would not need to hire additional staff to handle the AMP mandate as it had already beefed up its team, he added.
AMP Capital head of distribution George Carter said Salt was selected because of its ability to align with AMP's investment philosophy and process.
"Being a core manager, Salt is an extremely good fit for AMP Capital and our clients," he said.
"Salt has a proven investment team with extensive experience in managing the types of portfolios we offered for tender as well as having a truly integrated approach to responsible investing."
From next month, Salt will be the investment manager for AMP's NZ Shares Fund, Strategic NZ Shares Fund and Responsible Investment Leaders NZ Shares Fund, as well as the New Zealand equity component of the AMP Capital Income Generator Fund, AMP said.
Funds under management in those portfolios totalled approximately $690 million on February 28.
AMP said a number of active equity managers competed for the mandate and Salt was selected from a shortlist following on site visits and "extensive due diligence".
"We were impressed by the calibre and number of investment managers that expressed an interest in managing the portfolios," said Carter.