The party says it has some concerns about the deal, but on balance, it considers the agreement a good deal for Canada.
The Harper government has long accused the NDP of opposing free trade deals generally.
New Democrats say they won't sign on to any deal without seeing the details.
In the case of the Korean pact, which is now before the House of Commons, the NDP says it will level the playing field with other countries, such as the United States and the European Union, which have their own agreements with Korea.
It will also give Canadian companies a foothold in a key Asian market.
While the New Democrats will vote for the agreement, trade critic Don Davies said an NDP government would have gone for a better deal.
In a statement issued Wednesday, he criticized the government for including what he calls an unnecessary dispute settlement mechanism and for failing to win protections for the auto industry.
"The South Korean government aggressively promotes exports and their automotive industry," Davies said.
"Conservatives have been failing our country's manufacturing sector and must do more to ensure Canada's automotive sector has the support it needs to succeed in an increasingly competitive global market."
The Conservatives are touting the deal as a major lift for Canadian companies.
"This agreement is very important to Canada," Trade Minister Ed Fast told the Commons on Wednesday. "It is going to increase our exports by 32 per cent. We expect it to add close to $2 billion of economic activity to our economy."
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