Doni, who has 10 caps for Brazil, has been brought in as back-up to Liverpool’s current number one Pepe Reina.
A statement on the club’s website (www.liverpoolfc.tv) said the 31-year-old former international had signed a contract after agreeing personal terms and passing a medical.
Doni made 179 appearances for Roma in six seasons but has struggled to command a regular starting place at the Stadio Olimpico after falling behind Julio Sergio in the pecking order.
Liverpool’s director of football, Damien Comolli, said the move would help the club’s young goalkeepers gain experience.
“We are delighted to sign Doni,” Comolli said. “It’s a position we felt we had to strengthen because it will allow our young goalkeepers to go on loan and get some experience at some point during the season, which is crucial in their development.
“We are getting a very experienced goalkeeper who is used to handling the pressure of big games and international matches with Brazil. He had a very good end of last season with Roma, so we are very pleased,” he added on the club website.
Doni is Liverpool’s third summer signing following the arrival of England midfielder Jordan Henderson from Sunderland and Scotland playmaker Charlie Adam from Blackpool.
England winger Stewart Downing is also expected to join the Anfield club after Liverpool agreed a fee with Aston Villa on Wednesday.
