The 22-year-old has been with the club since the summer of 2010 as a Scottish Rugby Elite Development player, and has this term provided stiff competition to Dougie Hall and Pat MacArthur.
Gillies, a product of the Haddington and Heriot's clubs, played a leading role in the historic away win over reigning European champions Leinster in September, and has also had a say in the victories against Cardiff Blues, Dragons and Aironi. He came off the bench at Rodney Parade yesterday afternoon as the Warriors extended their unbeaten run in the RaboDirect PRO12 to six games.
Commenting on his new deal, the Scotland under-20 and Club XV forward told www.glasgowwarriors.org: "I'm really pleased to have been given a professional contract and I'm determined to make the most of this great opportunity.
"I've learned a massive amount from working alongside Dougie and Pat and under the guidance of [forwards coach] Shade Munro, and I've enjoyed contributing to some positive results in the opening months of the campaign."
Head coach Sean Lineen congratulated Gillies, saying: "Finlay thoroughly deserves this contract. He's worked extremely hard in his time here and has developed significantly as a player.
"He listens to advice, reads the game terrifically well and is another talented young guy who wants to help take this club forward."
Glasgow Warriors Elite Development coach Iain Monaghan added: "I'm delighted for Finlay. It's great to see guys progressing through the Elite Development system and benefitting from daily interaction with the core Warriors squad.
"Finlay has really earned this contract with his displays in the RaboDirect PRO12. It sends out a positive message to our other Elite Development players that if they step up and deliver when opportunities arise, they will go from strength to strength with the club."
Glasgow Warriors resume their European campaign this Sunday (11 December) when they take on Montpellier at Firhill in a crunch Heineken Cup Pool 3 fixture.
Supporters who book tickets via www.glasgowwarriors.org or by calling 0844 800 3490 by 8am on Sunday will save £5 on the standard match-day adult price of £20. Students/senior citizens £10, under-18s £5 (irrespective of when purchased).
Tickets are also available from the Gordon Street and Sauchiehall Street branches of Greaves Sports, our official retail partner, and at Firhill on the day.
Guinness PRO12
Suite 208, Alexandra House,
The Sweepstakes
Ballsbridge, Dublin 4, Ireland