Sunderland have completed the signings of Sebastian Larsson and Keiren Westwood on three-year deals.
The Black Cats confirmed last week that 26-year-old Sweden international Larsson would be playing his football on Wearside next season, but his move would not officially go through until 1st July following the expiry of his contract at Birmingham.
Larsson joins Ahmed Elmohamady, Connor Wickham and Ji Dong-won at the Stadium of Light, with manager Steve Bruce having made significant early progress in his rebuilding plan.
Bruce signed the former Arsenal trainee for Blues for £1million in January 2007 after a successful loan spell, and he went on to make 170 appearances.
However, he did not agree a new contract with last season's Carling Cup winners following their relegation from the Premier League and Bruce, who tried to sign him in January, has managed to get his man this time around.
The manager said: "Seb was a fantastic young player for me at Birmingham and he has matured into a very good midfielder.
"He has been courted by a number of top clubs over the summer - both in England and across Europe - so we are naturally delighted that he has chosen to come to Sunderland."
Larsson and his new team-mates are due to report for pre-season training next week, with the club pursuing further targets as they attempt to build upon last season's top-10 finish in the Premier League.
Sunderland have also confirmed their fifth summer signing after goalkeeper Westwood signed a three-year deal.
The 26-year-old Republic of Ireland international agreed a Bosman free transfer to the Stadium of Light last week, but the move could not be finalised until his contract at Coventry expired at midnight.
Westwood will initially battle with Belgian youngster Simon Mignolet for a place in Bruce's starting line-up, with £9million man Craig Gordon recovering from a knee injury.