"We're delighted to be part of LMI's world-class team and to be recognised for the expertise we bring to the partnership as well as our track record of successfully growing long-term investments," he said.
Les Mills International's fitness programmes are used in 20,000 clubs across 100 countries as well as being available for at home exercise through an on-demand streaming platform.
ACC will have two directors on the board while the Mills family will remain active in the business and would remain the majority shareholder.
Companies Office records show Philip and Jackie Mills and Brian Kreft owned 78.14 per cent of the company before the deal was done.
While the next largest shareholder was Antony Balfour, Brian Kreft and Robert Keogh with an 8.84 per cent holding.
Philip Mills, founder of Les Mills International, said he was excited to join forces with the ACC.
"It's the best of both worlds. We are going to get some fresh energy and expertise into the business with two new board members and the kind of financial backing that will help us access funding to execute further transformational growth initiatives."
The deal does not include Les Mills NZ, which operates a chain of gyms in New Zealand.
ACC has $47 billion worth of investments which its uses to fund the help fund the accident compensation scheme.
Of that, $2b is managed by its private markets team and is invested in a range of assets including property, infrastructure and private equity.
ACC has also recently launched a $50m impact fund that will invest in private companies involved in improving New Zealanders' health, safety and wellbeing, as well as targeting a high-investment return.
