George Santos has signed a three-month contract with Ipswich and has joined the squad ahead of their tour to Scandinavia.
Santos (right) swaps Grimsby's colours for those of Ipswich
The French-born defender, who can also play in midfield, was a free agent after coming to the end of his contract at Grimsby last season.
The 32-year-old started his league career in England with Tranmere in 1998, before moving on to West Brom and Sheffield United in 2000.
A team-mate of Marcus Bent at Bramall Lane, Santos made 69 appearances for the Blades.
He then joined Grimsby in 2002 on a free transfer, but failed to prevent the Mariners being relegated to Division Two.
"With John McGreal recovering from his knee injury and Thomas Gaardsoe picking up an ankle problem, I wanted to bring in someone else to help us at the back," Ipswich manager Joe Royle told the club's website.
Meanwhile, Grimsby have agreed a deal with former goalkeeper Aidan Davison.
The 35-year-old was the Mariners' number one goalkeeping target after Danny Coyne went to Leicester.
Davison has been training with the club and has agreed to sign a two-year contract on 1 August.