Brentford have signed 18-year-old Brazilian winger Gustavo Nunes from Gremio for a fee in excess of £10m.
The teenager has signed a six-year contract and the club has an option to extend the deal by two years.
“We have fought with other clubs [to sign him],” said Brentford boss Thomas Frank.
“He needs time to settle, but this is a very exciting signing. He is direct and he can create.”
Brentford are 13th in the Premier League after two games and entertain Southampton on Saturday (15:00 BST).
They have already signed Brazilian striker Igor Thiago, 23, for a club-record £30m this transfer window along with Liverpool’s Portuguese winger Fabio Carvalho, 21, in a deal worth £27.5m and Liverpool’s Dutch defender Sepp van den Berg, 22, in a deal worth £25m.
Meanwhile, Brentford and England striker Ivan Toney, 28, could leave the club before the transfer deadline at 23:00 BST on Friday.