Defence Minister Gerry Brownlee was told a few hours in advance of the attack.
Prime Minister Bill English says New Zealand was simply informed but not asked for its view.
Mr English says he understands the US taking action to prevent the chemical attack in Syria a few days ago occurring again.
He says the action is supported so long as it's proportionate.
Speaking to Larry Williams on Newstalk ZB, Mr English said he had been told that Mr Brownlee "was advised an hour or two before this attack".
"But we certainly weren't asked for our opinion on it.
"We've seen horrific attacks using chemical weapons which is against all international law.
"We of course would rather see the Syrian differences resolved by diplomatic processes but the Secuirty Council hasn't been able to condemn it or do anything about it so we can understand the US taking action to prevent that kind of chemical attack occuring again - and we support action as long as it's proportionate."
Earlier, Mr English appeared to be caught on the hop when asked about the US airstrikes.
He was visiting the Whangarei Town Basin and was unable to immediately comment when asked about the attack by reporters.
The Northern Advocate reported that English looked surprised and said he did not know anything about it.
His spokeswoman said the Prime Minister's office would be issuing a statement later in the day.
Foreign Affairs Minister Murray McCully said this afternoon it was becoming clear that Syrian Government forces were responsible for "outrageous" attacks in which chemical weapons were used.
"These events are horrific," he said in a statement. "It is critical that the international community emphatically demand an end to this violence, and that the Syrian government be held to account."
"In the absence of an adequate response from the United Nations Security Council, we can understand why the United States has taken targeted unilateral action to try and prevent further such attacks by the Syrian regime."
Security Council attempts to find a peaceful resolution in Syria have been vetoed by Russia.
While serving on the Security Council in December, New Zealand drafted a resolution to end airstrikes in Syria but it was voted down by Russia and China.
On Wednesday, Mr McCully condemned the chemical weapons attack in northwest Syria which prompted the US military response today.
The minister said he was "appalled" to learn of a new attack in an area where chemical weapons had previously been used.
The attack was "especially horrific" because of the number of children killed, he said.
"The Security Council must take action, or we will continue to see more horrific acts like this."
Labour leader Andrew Little was watching the situation unfold on CNN this afternoon as he waited for a jury to come back on his defamation trial.
Speaking about the missile strikes, Mr Little said: "It's already an incredibly complicated situation and this will only make it more complex."
