The documents were lost when Verga's son, Giovanni Verga Patriarca, lent them to a historian in the small town of Barcellona Pozzo di Gotto in Sicily who then refused to return them and hid them.
"The precious documents were never returned and attempts to retrieve them have always failed as they were very well squirrelled away," Antonio Coppola, who led the police operation, told AFP.
"The recovered material includes the first draft of 'The House by the Medlar Tree' as well as the manuscript of the first novel written by Verga in 1857 when he was 16 years old, 'Love and Homeland'," added Coppola.
In 1975, Verga's grandchild won exclusive rights to the missing manuscripts and agreed to sell them to the Sicilian city of Catania where the author was born should the documents ever resurface.
Police on the case caught a break when manuscripts by Verga appeared on an auction list at Christie's in Milan.
A raid on a house in Rome belonging to the historian's daughter, referred to by police only by the initials A. P., produced the documents.
"She now risks up to 10 years behind bars, or even more in the unlikely event that we find she is still hiding something," Coppola said.
Verga, who died aged 81 in 1922, was part of the Italian realist movement.
"The House by the Medlar Tree", inspired director Luchino Visconti's 1948 film "The Earth Trembles".
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