US soldier Bradley Manning has been found not guilty of aiding the enemy for handing over documents to Wikileaks.
He was found guilty of 19 of the other 20 criminal counts against him for the biggest breach of classified information in US history.
Army Private First Class Manning was accused of sharing more than 700,000 classified US files with Wikileaks.
The charge of aiding the enemy carries a penalty of life in prison without parole.
In March, the soldier pleaded guilty to lesser charges related to sharing the documents with the anti-secrecy website in 2010.
Manning, originally from Crescent, Oklahoma, opted to have his case heard by Judge Colonel Denise Lind, rather than a panel of military jurors.
Military prosecutors have called the 25-year-old soldier a "traitor" for publicly posting information that the US government said could jeopardise national security and intelligence operations.
The US government was pushing for the maximum penalty for the intelligence analyst's leaking of information that included battlefield reports from the Iraq and Afghanistan wars.
It viewed the action as a serious breach of national security, while anti-secrecy activists praised it as shining a light on shadowy U.S. operations abroad.
Army prosecutors contended during the court-martial that US security was harmed when WikiLeaks published combat videos of an attack by an American Apache helicopter gunship, diplomatic cables and secret details on prisoners held at Guantanamo Bay that Manning provided to the site while he was a junior intelligence analyst in Iraq in 2009 and 2010.
Manning, who early this year pleaded guilty to lesser charges that carried a 20-year sentence, will still be looking at a long prison term when the trial's sentencing phase gets under way tomorrow.
A crowd of about 30 Manning supporters had gathered outside Fort Meade ahead of the reading of the verdict.
The guilty verdict on most of the counts could make it difficult for WikiLeaks founder Julian Assange to persuade future sources of information to share classified details with the website.
Defence lawyers described Manning as well-intentioned but naive in hoping that his disclosures would provoke a more intense debate in the US about diplomatic and military actions in Iraq and Afghanistan.
More than three years after Private Manning's arrest in May 2010, the US intelligence community is reeling again from leaked secrets.
The secrets this time were exposed by former intelligence contractor Edward Snowden.
He has been holed up in the transit area of a Moscow airport for more than a month, despite US calls for Russian authorities to turn him over.
WikiLeaks founder Julian Assange has surfaced again as a major player in the newest scandal, this time aiding Mr Snowden in eluding authorities to seek asylum abroad.