"A major victory," the Swedish union declared.
The union has for several years been claiming that they have a majority of the workers behind them, but in the US more than half after needed for employees to gain the right to unionise.
The vote late on Wednesday saw some 77 percent of the around 300 staff at the factory in Danville, Virginia to vote for unionisation.
"The management has to understand that the serious issues at Swedwood have to be solved and we want to help them with that," said Bill Street at the Machinists Union to the Swedish local Smålandsposten daily.
Street has previously accused Ikea for management the plant as if it was a factory in a developing country, with low wages, poor working environment and irregular working hours.
Street was happy after the vote last night.
"I am more than satisfied," he said.
The issue has attracted a great deal of attention in the US media and Jon Stewart's Daily Show had its own take on the controversy in late June.