According to their lawyer, Muhammad al-Mutairi, on Tuesday, no evidence of any crime has been found and the court has dismissed the charges against the men.
"The case has been closed because there was no crime," he said. "The accusations were without evidence. The case is over."
Kuwait's military did not specify the number of soldiers involved in the plot when the arrests were made public in January. Other soldiers were detained were later released, and the details of the alleged plot were never publicised.
The military had no immediate comment on Tuesday's ruling. Kuwait has been a major Washington ally since the United States routed Iraq from the oil state in the 1991 Gulf War.
Hostility to US presence
Kuwait has served as the launch pad for the 2003 US-led invasion of Iraq that toppled former Iraqi president Saddam Hussein.
More than 18,000 American troops are stationed in this small oil-rich ally. More convoy into and out of Iraq everyday.
Nationals opposed to the US military presence in Kuwait have launched a number of small-scale attacks on US troops and civilians in the past three years, killing at least two people.
Earlier this year authorities clashed with groups allegedly planning more attacks on Westerners.
In an unrelated development, Kuwait's parliamentary human rights panel on Tuesday called for improving the detention conditions of suspected Islamist militants held in an American-style prison dubbed a "Kuwaiti Guantanamo."
"We want conditions improved in the new prison which is branded as the Kuwaiti Guantanamo," head of the panel MP Walid al-Tabtabai said, referring to the US naval base in Guantanamo Bay, Cuba, where hundreds of suspects are held.
The prison is built like American-style jails with heavily-fortified solitary cells, and detainees are not allowed to go out or read books and newspapers, the Islamist lawmaker said.
Parliamentary sources said that 23 inmates, all of them suspected Islamist fighters arrested following bloody clashes with security forces in January, are held in the new prison.
The panel also demanded that relatives and lawyers of the inmates should be allowed to visit them, Tabtabai said after a meeting with senior interior ministry officials to discuss claims of torture and mistreatment of detainees.