They among 150 people at the ceremony at the War Memorial Recreation Ground in Wannock Road on Remembrance Day.
Town mayor Steve Barber, town councillors, armed forces veterans, 60 children from Polegate Primary School and 10 students from Willingdon Community School combined cadets, some of whom were in uniform, joined them.
Members of the Polegate branch of the Royal British Legion, including the standard bearer, were also in attendance for the two minutes' silence.
The new plaque replaces one previously attached to the entrance gate of the recreation ground, which was removed many years ago.
The wording on it reads, "This land was gifted in 1922 by Rupert S Gwynne MP, Alfred P Wiggins and Clement Knight.
"To the Fallen in the 1914-1918 war whose names are inscribed within St. John's Church. Remembering also those who have made the ultimate sacrifice in all conflicts which have followed. We will remember them."
Sabrina Harcourt-Smith, one of six surviving grandchildren of Rupert Gwynne MP, told those gathered how her grandfather, together with his two associates Alfred Wiggins and Clement Knight, bought the land in 1922 to honour the 33 Polegate men killed in World War One.
She was accompanied by her husband, Lieutenant Colonel Charles Harcourt-Smith, as she unveiled the new plaque to warm applause. Rev Mark Lucas, of St John's Church, conducted a poignant dedication service, before a poppy wreath was laid by Corporal Andrew Black of the Royal Military Police.
Ahead of a two-minute silence, Royal British Legion bugler Richard Boswell sounded The Last Post as standard bearer Keith Hanks slowly lowered the Polegate Branch Standard.
Paul Woolmer, chairman of action group KORGI (Keep Our Recreation Ground Intact) which campaigned for the plaque to be restored and provided the plinth on which it is mounted, said, "The occasion was beyond everyone's expectation and turned out to be a true community event."
Mr Woolmer also thanked Christopher Whittick, senior archivist at the East Sussex County Record Office at Lewes.