Australia made it mandatory in 2011 for cigarettes to be sold in drab-looking packets that carry health warnings, reports the BBC.
Seven years on, the WTO has rejected complaints from four nations that the laws violate international trade.
Unless there is a successful appeal, the decision is expected to hasten similar regulations around the world.
"Australia has achieved a resounding victory," the government said in a statement.
Cuba, Honduras, Dominican Republic and Indonesia - all tobacco producers - had argued that plain packaging infringed on trademarks and intellectual property rights.
But the WTO rejected those arguments and assertions that alternative measures could achieve an equivalent benefit to public health.
The World Health Organization (WHO) praised the ruling, and said it would most likely "accelerate" the roll-out of similar packaging in other countries.
Six nations - Britain, Ireland, France, Hungary, Norway and New Zealand - have already followed Australia in introducing legislation since 2011.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
