Leaders from all 15 countries watched via video as Ministers signed the deal: from Auckland, Trade Minister Damien O'Connor signed for New Zealand.
Speaking afterwards, he told reporters it would bring security and certainty to exporters.
One of the aims in coming years is to progressively lower tariffs across many areas.
The pact will take effect once enough participating countries ratify the agreement domestically within the next two years.
A major power, India pulled out last year, claiming its key concerns about agriculture and domestic industry were not being addressed.
Trade analyst Stephen Jacobi said India's absence is disappointing for all participating nations and India itself.
The Ministry of Foreign Affairs and Trade said RCEP remains a potential gamechanger for trade in the Asia-Pacific region.
Group says treaty won't help NZ
But Edward Miller, from It's Our Future, fears New Zealanders won't benefit.
"We're seeing a huge secret agreement being negotiated where we don't know what the risks are and from the economic modelling that we've seen there's very little economic benefit to be gained.
"So we don't know why the government continues to do secret deals that are against our national interests."
Miller said there had been no effective public consultation over the deal, some parts of which attack New Zealand's national interests.
"The economic crisis that has come as a result of Covid is the biggest single economic event that we've had in New Zealand history.
"We need to preserve a policy space that will be able to ensure that we have a recovery that suits our people, our planet, our workers' rights etceteras. We can't guarantee that under RCEP."
Miller said It's Our Future would keep pushing the government to pull out of international trade deals.
