The company, whose headquarters are in Dunedin, had until now been wholly owned by staff.
But shareholders on Thursday approved a deal in which Sydney-based Mercury Capital acquired a 25% stake in the company.
In a statement, Forsyth Barr said the shareholding position was viewed by its board as “a natural next step in the company’s ongoing evolution”.
Forsyth Barr managing director Neil Paviour-Smith said initial discussions on the deal, which was first announced publicly in July, dated back a couple of years.
The company had reached a size where being 100% owned by staff was becoming increasingly challenging.
There was a “very strong consensus” from shareholders to find a capable and strategically-aligned party that could add value to the company.
“And we’re delighted its Mercury.
“It’s very exciting to get to the completion of what’s been quite a long process, but a good process.
“And otherwise, it’s just business as usual.”
Forsyth Barr was founded in Dunedin in 1936 and has a long-standing tradition of staff ownership.
The firm would remain majority-owned by more than 300 staff members alongside Mercury.
Mr Paviour-Smith said a lot of Forsyth Barr’s Dunedin staff owned shares in the company, from front-facing advisory staff through to administration, support and finance.
The company had acknowledged it could not continue to be 100% owned by staff, past and present, forever.
Mercury’s insights and experience from investing in many businesses across Australasia would be helpful going forward — whether that was around technology, wealth management or investment advice, he said.
Founded in 2010, Mercury Capital manages more than $2 billion in funds and provides growth capital to well-established businesses across Australia and New Zealand.
Its founder and chief executive Clark Perkins, and about half of its staff, are New Zealanders.