According to a Lebanese judicial source, the announcement of the death sentences was made on Friday.
The court "condemned to death Mussa Ali Mussa, who was found guilty of having contacted the Israeli enemy and passing on information," the source said.
The tribunal found that Mussa had passed on "information on officials from Hezbollah" to Israel between 2000 and 2010.
The court also sentenced Ali Sweid and Ahmed Hussein Abdullah to death in absentia on charges of spying for Israel.
On February 17, the Lebanese high court issued a death sentence to another Lebanese man found guilty of spying for Israel.
More than 100 people have been arrested in Lebanon on suspicion of collaborating with Israel’s Mossad intelligence agency since April 2009, including members of the security forces and telecommunications employees.
Many political figures have called for the death penalty to be imposed on people found guilty of being responsible for the death of Lebanese civilians, especially during the 2006 summer war.