The 35-year-old, who was released by Barcelona, has signed a one-year contract with City.
Hughes said: “Sylvinho has a wealth of experience at the very top level, having represented Brazil and played for some of the very top clubs in Europe.
“When the chance presented itself to bring him to Manchester City as a free agent, I saw it as representing excellent business for us.
“The lad won the European Cup last season and will strengthen our defensive options.”
