 In January 2006, as part of César's transfer, he went on loan to Lazio, which included an option to co-own the players rights at the end of season.On 11 August 2006, Siqueira joined Udinese in a co-ownership deal, for €750,000.Siqueira never became a regular for Udinese and made 3 starts and 13 substitute appearances in the 2006–07 season.