The youngster has been the subject of intense speculation over the past month, with up to six clubs reportedly interested in landing the services of the 19-year-old, who is also the subject of an eligibility fight between New Zealand and Queensland.
The extension means he will remain in Townsville for 2023, although the length leaves plenty to be desired, with the youngster seemingly not certain he wants to be a long-term Cowboys player.
That may hardly come as a surprise given the dearth of young talent the Cowboys have on the edge through Luki and Condon, but also the upcoming arrival of Luciano Leilua, who joins the club from the Wests Tigers in 2023.
The Tigers themselves were one of the clubs thought to be heavily interested in Nanai, although they will now likely turn their attention to off-contract Cronulla Sharks second rower Briton Nikora to join Isaiah Papali'i in 2023, who will play for the joint venture after his departure from the Parramatta Eels.
The Cairns junior, who has played eight NRL games, has already scored five tires, including four in four appearances this year.
Cowboys direct of football Michael Luck said he was "over the moon" with the contract extension.
“We are over the moon to be able to announce the extension of Jeremiah’s contract,” Luck said.
“As we’ve seen in the first eight games of his career, he is one of the most exciting talents in rugby league.
“We are thrilled to finalise the extension, which allows Jeremiah to concentrate solely on what is his first full season in the NRL and we will pick up long-term contract discussions later in the year.”