Kim Dotcom's legal team will take his fight against extradition to the Supreme Court.
The Court of Appeal has upheld the decision that the internet mogul can be extradited to the United States to face criminal copyright charges.
Mathias Ortmann, Bram van der Kolk, and Finn Batato can also be extradited, the court ruled.
Dotcom's lawyer Ira Rothken said he was disappointed with the Court of Appeal decision.
"We have now been to three courts each with a different legal analysis - one of which thought that there was no copyright infringement at all.
"We will seek review with the NZ Supreme Court."
A US grand jury indicted the group on February 6, 2012, over the now-defunct file-sharing website Megaupload, which allegedly shared pirated films and other media. It has been called the "Mega conspiracy" after several companies allegedly facilitated, encouraged and profited from significant mass infringement of copyright.
The US has sought the men's extradition ever since.
The group lost their case in the North Shore District Court in 2015 and has now lost appeals to the High Court and the Court of Appeal.
The group can seek leave to appeal the Court of Appeal's judgment to the Supreme Court.
If that fails the final decision as to whether the Dotcom and the other men will be extradited rests with Justice Minister Andrew Little.
The appeal court Justices Stephen Kos, Christine French and Forrie Miller found the extradition pathways the US rlied on were available to the US, and it had "tendered sufficient evidence to support their case on those pathways".
During the Court of Appeal hearing in February, lawyers for Dotcom and his associates argued the judicial process was flawed and the charges were not valid under extradition law.
One example, the court heard, was the failure to disclose the illegal spying by the Government Communications Security Bureau when applying for an arrest warrant.
In an FBI-ordered raid in 2012, police used the anti-terrorist Special Tactics Group in a helicopter assault on Dotcom's former Coatesville mansion.
The raid resulted in the 13 charges Dotcom and the group face, which include racketeering conspiracy, conspiring to commit copyright infringement and money laundering, and criminal copyright infringement.
This year, Dotcom also tried and failed to have former US President Barack Obama served with a subpoena and forced to give evidence in a New Zealand court over a damages claim for the streaming website.
Obama was in the country for three days at the time.
Dotcom argued that Obama could give evidence directly material to his proceeding, the purpose of the US' prosecution against him and its dealings with New Zealand authorities.
Last year, police are believed to have paid Dotcom a six-figure sum in a private settlement over alleged unreasonable force.
In a tweet sent during the past day, Dotcom said his "global legal team", comprised of 20 lawyers from New Zealand, United States, Canada, Hong Kong and Germany, has worked on his case.
He also tweeted yesterday that he had spent 165 days in court - and $40 million in legal fees.
