As a member of the under-20 Brazil team, Willian made his debut in the 2007 South American Youth Championship against Chile on 7 January 2007, which Brazil went on to win.
Sebagai anggota dari tim U-20 Brazil, ia melakukan debut di Kejuaraan Pemuda 2007 Amerika Selatan melawan Chile pada tanggal 7 Januari 2007, yang Brazil memenangkannya.