Barker spent two seasons with Glasgow - in 2004/05 and 200/5/06 - before joining Irish province Ulster for a season en route to his current club, French Top 14 side Castres.
On his return to Glasgow, 6ft 6in 18st Barker said: "I'm very excited to be coming back to Glasgow because I thoroughly enjoyed my previous spell with the club.
"Glasgow have been improving every year in Europe and the Magners League and I'm impressed with the ambition Sean Lineen has for the team.
"I can't wait to get back to Glasgow and play the best rugby of my career."
Warriors head coach, Sean Lineen, added: "It's a real coup getting Tim back to Glasgow. He'll help drive the competition we've got going in the second row.
"Tim will give us that hard edge we need and will increase the mobility of the pack."
In addition to his club achievements, Barker has represented Ireland at U18, U19 and U21 levels.
Now that Tim Barker has signed up with the Warriors, it's your turn too. Season tickets for the 2008/09 campaign are now available with prices frozen for adults, remaining at £150, a saving of £65 compared to buying tickets for individual games. That's the equivalent saving of four free games!
A new structure has been implemented for concessions and under-18s.
The concession ticket will be available to students and OAPs, priced at £80, with supporters under the age of 18 getting to see 13 games of top-flight professional rugby for only £30, the equivalent of just £2.30 per game.
In addition to the new season ticket pricing, Warriors fans will also receive additional benefits.
Firstly, season ticket holders will be able to attend the pre-season friendly against Bristol on Friday 22 August and the away Magners League fixture against Edinburgh at Murrayfield free of charge.
Also included is the opportunity to attend a Partick Thistle league game at Firhill absolutely free (more details of this offer will follow in due course).
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