The deal - which sees Harley remain with the club until at least the summer of 2022 - is a major boost for Dave Rennie's side, as they get ready to host Zebre this Friday night in a crucial Guinness PRO14 match at Scotstoun.
The only player to have made over 200 appearances for the Warriors, the 29-year-old flanker surpassed Graeme Morrison as Glasgow's record appearance maker in February 2018.
He played an incredible 23 games in a row for the club, a run which included 18 consecutive starts from December 2018 until November 2019.
Harley made his Warriors debut in the opening match of the 2010/11 season against Leinster, going on to claim the club's Player of the Season award at the end of his debut campaign as a professional.
He quickly became a key member of the club's leadership group, captaining the squad for the first time against Ulster in the opening match of the 2011/12 Guinness PRO12 season in Belfast.
Equally as comfortable in the second-row, the former West Of Scotland man has scored 11 tries for the club in his career to date including the opening try of the 2015 Guinness PRO12 Final triumph over Munster.
Harley has also represented his county with distinction; the flanker has earned 21 caps for Scotland in his career to date, including scoring the match-winning try on his debut against Samoa back in 2012.
He has made 15 appearances so far this season, most recently in the Heineken Champions Cup victory over Sale Sharks - a game that saw him play his 50th match in Europe, to equal Gordon Bulloch's club record for European appearances.
Speaking to glasgowwarriors.org, Harley said: "There were a lot of factors in deciding to stay. First of all, Glasgow is where I grew up - when I was younger, I'd come down and watch the team. I've got a lot of fond memories of going along to games at Hughenden, and then growing up and playing at Firhill and Scotstoun.
"We've got a good group of guys here as well - it's always fun to come in and train, and then play alongside those guys. I'm glad that I'll be around for the next couple of seasons.
"The focus is still very much on this year, but I spoke to Danny (Wilson) a bit before re-signing about his plans for next year. Keeping the focus on this season is first and foremost for us right now though.
"The support of the Warrior Nation is massive. I remember growing up we'd have two or three thousand at Hughenden and then similar numbers when I started playing at Firhill. The support over the last ten years has gone from strength to strength - we win most matches we play at Scotstoun, and a large part of that is because we have the fans behind us. The atmosphere they create is incredible and it's great to have their backing as a home player.
"I don't have a target (for appearances) - I just want to play as many games as I can for Glasgow."
Glasgow Warriors Assistant Coach, Kenny Murray said: "Rob is one of the hardest working and most professional players that I've seen at my time with the club.
"Glasgow Warriors means a lot to him and you can see it in his work rate, attention to detail and professionalism on the pitch.
"It's great he's chosen to stay with us for another two years and we’re looking forward to seeing him continue to add to his all-time appearance record."
Incoming Glasgow Warriors Head Coach, Danny Wilson added: "Rob has been with the club a long time and we're really pleased that he has decided to stay. He has so much experience, having made 227 appearances and he'll be a real asset for us over the next couple of years."