The Ministry of Foreign Affairs and Trade spent more than $4 million sending staff around the world to negotiate the Trans-Pacific Partnership trade deal.
Documents obtained by Checkpoint with John Campbell show the ministry spent nearly $2.5m on flights alone, not including the travel costs of the two ministers themselves.
US President Donald Trump killed the 12-country deal when he pulled his country from it.
Trade Minister Todd McClay said he did not know the total cost of negotiations, but it was money well spent.
"My view is that if New Zealand's not out arguing for better rights and fairer access for New Zealand exporters overseas and making the case on our behalf, nobody will."
He said he believed the TPP could be renegotiated without the US.