Seven players from Udinese and one from Granada, clubs owned by the Pozzo family, have moved to Vicarage Road for undisclosed fees.
After successful loan spells in 2012-13, midfielders Almen Abdi and Cristian Battocchio, and defender Marco Cassetti have all moved to Watford permanently from Serie A side Udinese.
Abdi and Battocchio have signed contracts with Gianfranco Zola's side until 2016, while Cassetti returns on a one-year agreement. Meanwhile, Granada's Daniel Pudil has signed until 2017.
The remaining four new signings all come from Udinese. Defenders Gabriele Angella and Marco Davide Faraoni will provide more cover at the back, while forwards Diego Fabbrini and Javier Acuna will attempt to fill the void left by top goalscorer Matej Vydra.
Angella and Faraoni, both Italy under-21 internationals, have agreed five-year deals until 2018.
Fabbrini, a full Italy international, joins until 2017 while former Real Madrid B striker Acuna arrives on a three-year deal.