The 38-year-old has spent the last two-and-a-half years with the Latics, helping them win promotion back to the EFL in 2025.
Garner, who spent one season at Portman Road in 2017/18, now links up with Adam Lakeland's side after signing a one-year deal with the option of a further year with the Shrimps.
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Joe Garner helped Oldham win promotion to League Two at Wembley in 2025. (Image: PA)
He will look to help the Lancashire based club bounce back after relegation from the National League last season.
"It's a massive club and we're looking to push on this year to get out of the league,"Garner said.
"We know it will be difficult but we'll give it our best shot. I'm happy everything has been done so fast, so I can get out there with the lads. It's going to be a massive pre-season."
The veteran frontman bagged ten goals in 32 games for the Blues, following his arrival from Rangers in the summer of 2017.
Garner left Town a year later to join Wigan Athletic in a £1 million deal, before a spell in Cyprus and then stints at Fleetwood Town and Carlisle United.
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