The 35-year-old Uruguayan's deal at the Ciutat de Valencia was set to expire at the end of June and, after revealing a tentative agreement was in place last month, the Serie A club have officially secured the experienced keeper's services until June 2015.
A statement published on violachannel.it read: "Fiorentina announce the signing of Gustavo Adolfo Munua Vera.
"The Uruguayan goalkeeper was born in Montevideo on January 27, 1978 and played for Levante last season."
Munua made a total of 139 appearances in the Primera Division with Levante, Malaga and Deportivo La Coruna after leaving Nacional in 2003.
He collected 21 caps for Uruguay and travelled to the 2002 World Cup as back up for Fabian Carini.