More than 30 people attended the ceremony at the Anzac memorial at Lake Hawea on Sunday, including relatives of the soldiers.
The two privates, John Alexander Barclay (36) and John William Kingan (21), both of Hawea Flat, were killed in action at Polderhoek Chateau in Belgium, after a failed attack on German positions.
Wreaths and poppies were laid for both men.
Anne Wade, a niece of Mr Kingan, said she had only recently found out her uncle had died in the war.
"Our parents never said anything about it, so it's quite an emotional day for us.''
Ken Allan, of the Upper Clutha Historical Society, said the two men, and several others around the district, had not been known by the community as having fought, and had been left off the local memorials.
Only through years of research had the society discovered the history of many soldiers from around the area.
-Sean Nugent
