The 26-year-old Ghana international, who left Portsmouth for Inter in a ?12million move in July 2008, will join compatriots John Mensah and Asamoah Gyan at the Stadium of Light.
Loan move: Muntari
Bruce said: 'Sulley is a fabulous acquisition for the club. When the opportunity arises to bring in a player of his ability - even in the short term you have to take it, and I'm delighted that we have been able to.
'His adaptability is a great asset. He did extremely well at Portsmouth so he knows the Barclays Premier League well and you have to be some player to move to Inter Milan for the fee that he did. He's a great addition.'
Muntari has slipped in the pecking order at Inter after playing a key role under former boss Jose Mourinho.
Sunderland have taken advantage of that to snap up a player they have been trailing for some time.
Bruce admitted his interest in the Ghanaian and Paris St Germain's Stephane Sessegnon before Darren Bent stunned the Black Cats before handing in the transfer request which ultimately led to his departure for Aston Villa.
The club now hope to push home their interest in Sessegnon after days of difficult negotiations, but the manager will be relieved to have finally got at least one of his transfer targets.
Meanwhile, Sunderland have given Spanish side Real Zaragoza permission to talk to Paraguay international defender Paulo da Silva over a move to La Liga.
Fuller's Sunderland switch edges closer as player discusses ?3m moveReal Zaragoza close in in Sunderland defender Paulo da SilvaAll the latest Sunderland news, features and opinion
Explore more:People: Darren Bent, Steve Bruce, Jose Mourinho Places: Paraguay, Ghana