Donald Trump in power could increase tariffs and make trading difficult, Federated Farmers vice president Anders Crofoot says.
Mr Crofoot said the election was bad news for the primary sector.
"The TPP, that'll be dead in the water, but the writing may have been on the wall for a while now with both candidates campaigning against that.
"It's not great that one of our big trading partners is anti-free trade, on the other side of that the president doesn't call all the shots."
That echoed Prime Minister John Key's take on the TPP's future, saying it was not happening in the short term.
Mr Trump pledged to unpick several free trade deals during his US presidential campaign. One of his close supporters said last night, after his victory, the deal was now dead.
Mr Crofoot said New Zealand farmers were worried.
"There are some big concerns, things like the TPP had a lot of benefits for New Zealand as a trading nation."
Tariffs were another area of uncertainty.
"Whether they become protectionists and start whacking tariffs on remains to be seen," he said.
"My hope? That would be Trump as a businessman surrounds himself with good advisers and one can hope that he will heed their advice."
Federated Farmers dairy chair Andrew Hoggard said it was hard to tell what would happen as there was no mention of agricultural policy during the campaign.
He said the US election results could hit Fonterra because they launched their "trusted goodness" brand this week.
"Some of that is about better positioning of product in the US market, with [the] potential of TPP there was going to be more access around infant formula powders, so there could have been some big gains there."
It could be bad news if the global economy became depressed, or if prices fell back globally with the US going into a trade war with China, Mr Hoggard said.
"That could see Chinese incomes drop, which as a big customer of ours for milk powder then it could have a big impact there."