Bertoldo, Bertoldino e Cacasenno was the first comic opera, which opened the Venetian era in the history of opera buffa. Contemporary dictionaries name Carlo Goldoni (text) and Vincenzo Legrenzio Ciampi (music) as its authors. The detailed review of the manuscript (preserved in the Estense Library in Modena) undertaken in the article for the first time, reveals the original “pasticcio” nature of this opera. An analysis of the handwriting and various markings shows that the score contains musical material representing two different productions of the opera: the Venice premiere in 1749 and a performance in London in 1755. Ciampi, who wrote about one third of all the musical numbers for the Venetian premiere of the opera in 1749, was apparently joined in his work by other composers. For the London production in 1755 Ciampi added a newly composed portion of musical numbers, however, still almost a quarter of the entire score remained consisting of insertions of music by other composers. The surviving music also makes it possible to establish exactly what material from the Venetian production was used in the parodies on this opera composed in Paris: Bertholde à la ville by Louis Anseaume (1754) and Le Caprice Amoureux, ou, Ninette à la cour by Charles-Simon Favart (1755). The study of Bertoldo, Bertoldino e Cacasenno expands our understanding of the practices of opera buffa at the early stage of its history.