Barnes, who was primarily a right tackle his first four seasons in Oakland, started the first 11 games at left tackle last season before moving inside to left guard when Jared Veldheer returned from left triceps surgery in training camp.
"I'm so excited to be back," Barnes said in a team-issued release. "I'm going on my sixth year here, and we've had some ups and downs but there are some unfinished things we have to do here. I want to be a part of the process that turns this thing around. ... I am just excited I get the chance to come back and help this team win."
The 6-foot-6, 321-pound Barnes, who turns 32 on April 21, spent the first four years of his career in Jacksonville after the Jaguars selected him in the second round (No. 52 overall) of the NFL draft out of Washington in 2005. He joined the Raiders as an unrestricted free agent in 2009.
Terms of this contract are unknown, but he has said he's been on one-year contracts since his arrival in Oakland.
Barnes has started the last 41 games in which he's played for the Raiders, including last year when his wife gave birth the morning of Oakland's game against the Philadelphia Eagles on Nov. 3. He has appeared in 63 games, with 46 starts, as a member of the Raiders. In his career, he has started 103 of 123 games.
Earlier this month, the Raiders re-signed exclusive rights free agent Lamar Mady, a rookie guard who played in seven games.