New Zealand Sotheby's International Realty agent, Ian Keightley, said he has been asked to keep the price and the buyer's identity confidential.
Keightley said there was a "multi-offer sale" involving two New Zealand buyers.
"Covid multiplied inquiries, I'd say by one thousand per cent. We had a lot of interest from expats but people couldn't travel, so that was a difficulty," Keightley said.
The 518-hectare island is currently a sheep farm and offers private accommodation in three small baches scattered around the property. It also includes an "expansive seven-bedroom weatherboard farmhouse" according to Sotheby's information. The farmhouse is occupied by farm manager, Andrew Newton.
Keightley said the buyer intends to "continue the current farming operation, tourist accommodation business, maintain current public access and further explore the establishment of strategic environmental areas across the island."
Pepin is connected to the mainland by a naturally occurring boulderbank causeway and a road, owned and maintained by the Nelson City Council.
The road connects both the Pepin Island property (which is freehold land) to the mainland and also the popular Cable Bay beach, where the public have access to the island up to the high tide mark.
Nelson-based National list MP Nick Smith had seen the prospective sale as an opportunity to extend public access to the island's coastline. However, the sale to domestic buyers precludes the change.
A sale to an overseas buyer, under overseas investment provisions, could have allowed the extension of public access to a Queen's Chain reserve of an additional 20m above the tide mark.
Smith said he welcomed news of a New Zealand buyer for "an iconic part of Nelson with a unique history through the original telegraph cable connected in the nineteenth century through [adjacent] Cable Bay."
Smith said depending on the new buyer's plans there may still be the possibility for the addition of a Queen's Chain reserve; subdivision would also trigger the requirement to release this reserve.
Nelson Mayor Rachel Reese had hoped the government would acquire the Island through the Department of Conservation.
Reese wasn't immediately available for comment on Wednesday.
In recent years the island's circuit track has been open to the public, as a local fundraiser, for one day over the Queen's Birthday weekend in June.
The island's coastline, Tasman Bay on one side and the tidal Delaware Bay estuary on the other, is popular both with kayakers and boaters.
It's also an area of significant interest to local Maori, and was captured and contested by several tribes through the 1800s.