His work is held by many collections and stands in public places in Greece and elsewhere, including his sculpture "The Runners" at O'Hare International Airport in Chicago.

In 1967 he was given a state scholarship to study Ancient Greek Art in Greece, Egypt, Turkey, Cyprus, Sicily and Southern Italy.

[3] After retiring, in 2009 Papagiannis founded the Theodoros Papayannis Museum of Contemporary Art in a former school in his home town of Elliniko.

Every summer students and sculptors are invited to the museum to create sculptures, which are placed on the 5 kilometres (3.1 mi) route from the village to the Monastery of Tsouka.

His work includes busts and statues of prominent personalities, medals, coins and large sculptural compositions.