Riveros joins Black Cats
The 27-year-old, who has been playing his club football in Mexico with Cruz Azul, has put pen to paper on a three-year contract.
Bruce said: "We have been monitoring Cristian for a while now, so I'm delighted to have concluded a deal which will bring him to Sunderland and the Barclays Premier League. He is a very creative midfielder and a player that will enhance our attacking options from wide positions for next season."
Bruce revealed last week that he was quoted £12million for Riveros when he first tried to sign him during his time at Wigan, although details of any fee have not been released.
The midfielder, full name Cristian Miguel Riveros Nunez, joins compatriot Paulo da Silva at the Stadium of Light, and both men are expected to go to the World Cup finals with Paraguay this summer.
Riveros moved to Cruz Azul in July 2007 after spending his formative years in the game in his native country, by whom he has been capped 45 times and scored eight goals.
He said: "The league is very competitive and Sunderland have shown trust in me as a person and as a footballer. The history here is good and I'm delighted to be joining the club."
Bruce said on Friday he hoped to push through the deal within a week, and spoke highly of the player.
He said: "We have been working a long time on Riveros. I tried to sign him two years ago - I was quoted £12million and couldn't afford him. He's a middle of midfield player who can play on either side as well and something different to what we have got."
Bruce has prospered in the Central and South American markets in recent years with the likes of Wilson Palacios, Antonio Valencia and Maynor Figueroa, but admits it often takes imports from that part of the world time to settle into the English game.