BlackRock, an international investment management firm based in the United States, has taken a stake in Telecom.
BlackRock has disclosed it has a stake of 5%, or 96 million shares.
Telecom will split into two at the end of the month, with its network arm, Chorus, and retail business, New Telecom, becoming stand-alone listed companies after receiving shareholder approval.
There has been speculation that New Telecom will be a takeover target.
At last month's annual meeting, Telecom's departing chairman Wayne Boyd said removing the burden of regulation means the retail arm is well-placed to exploit its still-dominant position in the phone market.
Telecom stock rose 4.5 cents to $2.66 per share on Friday morning.