A sign which reads 'Trump War Minerals HQ' with a cutout of a bald eagle preying on a kiwi was also put up outside the office in the suburb of Botany this morning.
Greenpeace has claimed responsibility.
In a statement, campaigner Juressa Lee said they were protesting a potential deal for New Zealand to supply rare and critical minerals to the US.
She said a minerals deal would lead to more mining projects, causing "environmental destruction", and also make New Zealand complicit in the war in the Middle East.
"We know a minerals deal would be bad for the land and sea of Aotearoa. But since the United States and Israeli governments launched a military attack on Iran in clear breach of international law, the stakes are even higher.
"We're calling on Luxon to say no to a minerals deal with Trump. We're also inviting the public to show their strong opposition to this deal if they're concerned about complicity in warmongering and the exploitation of our environment for military aggression."
Luxon has previously said New Zealand is among more than 40 countries talking to the US about supplying minerals, and no Cabinet decisions have been made.
