The 25-year-old Nigerian is Keane's fifth summer signing and takes his investment so far this summer to around £16million.
Etuhu arrived on Wearside on Tuesday morning for a medical and has signed a four-year contract.
Keane told the club's website: "I'm very pleased that Dickson has signed. He will add competition to oursquad and give us a real physical presence.
"He's a big, strong player who can also get a goal."
Keane has been busy in the transfer market and his spending has not ended yet.
"We're definitely heading in the right direction as far as getting the players we want to the football club.
"The signing of Dickson creates competition and a club like Sunderland needs that. We all talk about the big four having competition for places, I feel every club should have it and that's what I'm trying to do here," added Keane.
Central midfielder Etuhu was born in Nigeria, but raised in London, and attended the same school as new team-mate Nyron Nosworthy.
He began his career at Manchester City and secured a £300,000 move to Preston in 2002 before joining Norwich for £450,000 after a successful loan spell in January last year.
The Black Cats open their pre-season campaign at neighbours Darlington tomorrow evening, although Keanne today revealed Chopra and Richardson are unlikely to be involved, meaning Etuhu may also have to wait for his debut.