The contract is worth up to $2.1 million with incentives, a league source told ESPN NFL Insider Adam Schefter.
One of coach Mike Singletary's priorities has been to bring some continuity to a unit that was plagued by injury last season -- and Sims filled in admirably as the starter at left tackle for seven games when Joe Staley was sidelined with a knee injury.
The 6-foot-5, 300-pound Sims is an 11-year NFL veteran who spent the past two seasons with San Francisco. He appeared in 30 games and made 15 starts, including eight at right tackle in 2008 in place of the injured Jonas Jennings.
Sims expects to play a similar fill-in role in 2010 for the 49ers, who finished 8-8 and ended a franchise-worst stretch of six straight losing seasons.
"Yes, I assume that would be the case, to provide depth and with my experience, be able to play both sides and really help the younger guys develop a little quicker," Sims said. "We have such a great group of guys, especially on the offensive line, that I really look forward to working with those guys."
Sims, 35, spent his first nine seasons with the Oakland Raiders after a standout college career at Utah.
Information from The Associated Press was used in this report.