ESPN.com has learned that the deal is for one year and $730,000.
Archuleta was at the Raiders facility Monday morning and left with trainer Rod Martin to take a physical. Oakland released safety Greg Wesley to make room on the roster.
"I was just waiting for the right opportunity and the right team to play for and they came with some interest so I'm happy to be here," Archuleta said after his first practice Monday night.
Selected by the St. Louis Rams as a safety in the first round of the 2001 draft, Archuleta plans to try to make the Raiders as an outside linebacker. For more than a month, Archuleta had been talking to the Tennessee Titans about being a weakside linebacker.
"I enjoy playing in the box," he said. "That's what gets me jazzed up so I decided I was going to try to make a run at linebacker."
Some of his best days in the NFL were in St. Louis when he played for defensive coordinator Lovie Smith, who built a defense around Archuleta's speed and play-making ability as a safety-linebacker.
At Arizona State, Archuleta was a 210-pound linebacker with great speed and a great workout ethic. His hope in signing with the Raiders is resurrecting his career.
The Raiders will be his fourth stop in the NFL. He played for the Rams from 2001 through 2005. He joined the Washington Redskins in 2006, receiving the largest contract given to a safety: $30 million for six years, with a $10 million bonus. But he was traded to the Chicago Bears the next season. He broke a hand early last season and started in just 10 of the 15 games in which he appeared. He lost his starting job to Brandon McGowan and finished the season on special teams.
He hopes that his change in positions will spark new things for his career.
"We're going to play him at linebacker and special teams and see what he can do for us," coach Lane Kiffin said. "We worked him out this morning and he moves around extremely well. He was in very good shape so we're going to give him a chance."
Kiffin said after the morning practice that he wanted to bring more players into camp to create more competition for jobs and improve the team's depth.
"It's been a situation that unfortunately, we haven't brought guys in," he said. "I control what I can control, come out every day and get our guys as good as we can. I'm pleased with the top of our roster but we need to add to the bottom of our roster. We need more competition."
Archuleta has started 86 of his 103 games in the NFL, making 423 solo tackles and intercepting four passes.
"He's a great guy with talent, a good nose for the ball, he brings a lot to the game. I'm excited to have him here," said Thomas, who played with Archuleta in St. Louis. "He can cover tight ends, play defense, play the run, so I'm excited to have him."
Wesley was signed the week before training camp to provide a boost to the secondary but was limited by a back injury before being released.
John Clayton is a senior writer for ESPN.com. Information from The Associated Press was used in this report.