The 28-year-old, who played in the Premier League in the 2010-11 season while at Blackpool, joins the League Two club after impressing on trial.
Boss Danny Cowley told the club website: "Technically and tactically you can see he's played in the Premier League and will be a good role model.
"He's one of those that makes everyone around him 5% better."
Eardley, who won the last of his 16 Wales caps in 2011, left League One side Northampton Town at the end of last season.
Find all the latest football transfers on our dedicated page.
Lincoln City have signed former Wales international right-back Neal Eardley on a deal until January.