It also owns the franchise for the Burger King chain and chemical business Ixom here.
Of its investment into Partners Life Moorjani said it had been impressed with the growth achieved by the company as well as the quality of its management team and customer centric approach.
"Given Blackstone's experience in the insurance sector, we look forward to supporting the company in achieving its strategic objectives and maximizing value for all shareholders."
Partners Life managing director Naomi Ballantyne said the investment meant the company's medium term capital requirements would be satisfied without having to go to back to equity markets to raise more money.
"The $200 million is all new capital, meaning existing shareholders will remain co-invested alongside Blackstone."
Ballantyne, who has successfully helped establish and sold two previous insurance companies in New Zealand, said it intended to publicly list the company when market conditions were right.
"The best possible endorsement of our business is to have a world-leading organisation like Blackstone join us in achieving our goals, which can now become significantly more ambitious thanks to this substantial investment.
The investment in Partners Life is subject to shareholder and regulatory approvals.