Cpl Reginald Robbins's name was on the roll of honour read out at the original unveiling ceremony for Andover's war memorial in 1920.
It it not known why it was never included on the actual memorial.
A service of rededication was held after his name was inscribed on the Portland stone monument.
Cpl Robbins was born in Sussex but moved to Andover with his father when he was in his teens, joining the Royal Engineers in 1917.
He saw service in France and Egypt before his death from Spanish flu in 1920 at the age of 25.
The disease claimed up to 50 million lives around the world during the pandemic which began in March 1918.
Leader of Test Valley Borough Council, Councillor Ian Carr, said the inscription, which followed research by local historian Craig Fisher, was a "poignant tribute".
"We may never know exactly why Reginald's name was not included on the memorial, but it is important that he is honoured and correctly remembered alongside the other local servicemen who gave their lives," he added.
The name of a soldier who died in the years following World War One has been added to a Hampshire war memorial, 95 years after it was erected.