The 20-year-old, who has penned a three-year contract after the clubs agreed a fee reportedly in the region of €2m, made his first-team debut for Banfield in 2002/03 but only became their first-choice goalkeeper at the start of last season.
It is unclear when Barbosa will leave his homeland to move to Spain, as Banfield are still involved in the Copa Libertadores. He is expected to replace José Reina at Villarreal, with the 22-year-old being strongly linked with a switch to European champions Liverpool FC.
Villarreal finished third in the Primera División in 2004/05 to earn a place in the third qualifying round of the Champions League. On Monday, they completed the €1.8m transfer of 18-year-old Ecuadorean international midfielder Luis Antonio Valencia.
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