Mostto, 29, who played for Cienciano in Peru, is reported to have cost the Tykes in the region of £350,000 and is in his country's national squad for the imminent Copa America. Oakwell boss Simon Davey believes his side got something of a coup.
"We had to fight off a lot of competition for his signature from Norwich and Leicester as well as a Turkish club," said Davey. "He was identified to us by a contact of mine. I watched him and was very impressed."