The ruling is unlikely to set a precedent for such prosecutions, Stars and Stripes reported Monday.
Pvt. Lazzaric Caldwell had been convicted of disrupting order and discrediting the Marine Corps after he slashed his wrists in 2010 in his barracks at Camp Schwab on the Japanese island of Okinawa.
In reversing Caldwell's conviction, the U.S. Court of Appeals for the Armed Forces ruled he had been improperly charged.
Caldwell had pleaded guilty at his court martial to disrupting Marines in his unit who gave him emergency medical care and discrediting the service through his attempt at killing himself.
His defense attorney, Lt. Mike Hanzel, argued at his appeal that Caldwell suffered from post traumatic stress disorder, depression and brain seizures and should not have been allowed to plead guilty without a psychological examination.
The high court found that exposing other Marines, including a medical corpsman, to his blood and the use of medical supplies in his treatment did not in itself undermine "good order and discipline." The court also ruled the military was not justified in charging that the suicide brought dishonor to the Marine Corps.
The court denied the Caldwell decision would set a precedent, noting it had upheld other prosecutions of attempted suicides.