The scrum-half returns to Scotstoun following a successful loan spell during the 2012/13 season, when the 28-year-old made seven appearances for the club. As part of the deal he will be available to play for Stirling County's Super6 team when he's not selected for the Warriors.
Capped by Scotland at U20 level, Kennedy made his Glasgow Warriors debut in a 22-19 win at home to Zebre in September 2012 and he came off the bench in the 27-20 win over Northampton Saints at Scotstoun in the Heineken Cup in January 2013.
His livewire style and crisp distribution made him a valuable asset, with the scrum-half's form seeing him earn a first senior international call-up ahead of the 6 Nations in 2013.
Whilst yet to earn a cap at senior fifteen-a-side level, Kennedy has represented his country with distinction in the abbreviated form of the game, running out for Scotland 7s at 11 World Rugby Sevens Series tournaments.
The most recent of those appearances came at the 2019 Hong Kong Sevens, where he touched down for a try in the group stage victory over Japan en route to helping his side lift the Challenge Trophy.
Kennedy has also represented Edinburgh and London Irish, after coming through the ranks at Alloa RFC and Stirling County.
He made 66 appearances for Richard Cockerill's side during a seven-year spell in the Capital, which came to an end last season.
Speaking to glasgowwarriors.org, Kennedy, said: "It's been really good to get back involved with the boys.
"Training has been going really well - I've enjoyed getting to know all of the boys, as well as Dave and Jason. I'm lucky I know Kenny and I've worked with John Dalziel with Scotland 7s.
"When I was here on loan before I didn't play that much, but I really enjoyed myself. The style of play that Glasgow favour was a massive factor in my decision to come back - obviously different coaches will have different focuses, but I loved watching the free-flowing attacking play and I want to be a part of that. It's always been a part of the game I enjoy, trying to get to breakdowns as quickly as possible and keeping that tempo high.
"I came through the ranks at Stirling County, from Under-18s right up until I signed full-time with Scotland 7s, so it’'ll be great to get back there too.
"With Super6 on the way, I'm hoping we can do something special. I'm excited about it, especially the cross-border element of the competition. With boys being semi-pro now, the standard should be that bit higher, so it's a great prospect."
Glasgow Warriors Assistant Coach, Kenny Murray, said: "Sean is an exciting player who really suits our style of play. His speed around the pitch and the speed of his pass has the ability to really stretch defences.
"He is also very dangerous around the fringes and Glasgow fans saw glimpses of what he is capable of when he made a good impression here back in 2012.
"He'll provide valuable depth in a position which we expect to be depleted in for large chunks of the season and will compete to be involved even when we are at full strength."
Stirling County Head Coach, Ben Cairns, added: "We are thrilled to secure the services of Sean in partnership with Glasgow Warriors as we enter the inaugural Super6 season.
"Since coming into my role as Head Coach of Stirling County we have had a recruitment policy of looking at home grown guys first. Sean is a local guy, who wants to play for County and whilst we hope he pushes for selection at Warriors on a weekly basis, we look forward to him pulling on the County Super6 jersey when he's released to us by Glasgow.
"He will bring some valuable experience to our young side and it's a signing which I am sure will excite our other recruits, the County faithful and the wider community."