The Scottish international stand-off will return to Scotstoun after spells with Edinburgh and Worcester Warriors.
A storming 2011/12 campaign saw him named in the then-RaboDirect PRO12's Dream Team, scoring 198 points to help the Warriors to the semi-finals.
Weir also contributed to Glasgow's PRO12 title-winning campaign in 2014/15, coming off the bench to slot a penalty from 40 metres in the 31-13 win over Munster in Belfast.
His final appearance at Scotstoun prior to joining Edinburgh in 2016 involved a flawless kicking display that saw Weir record 10 conversions from 10 attempts in a 70-10 win over Zebre, with the fly-half also crossing for a try.
A three-year stint at Worcester Warriors followed in 2018 and saw the fly-half quickly become a cult hero with the Sixways faithful, notching over 400 points for the English outfit.
His Worcester career has included being one of only two players to amass over 200 English Premiership points in 2018/19, joining England fly-half George Ford in the exclusive club.
In addition to his exploits on the pitch, Weir's keen support of Acorns Children's Hospice saw him raise over £16,000 by growing his unmistakable afro at the end of 2020.
His career to date has also seen the fly-half represent his country with distinction, registering 80 points from 30 Scotland appearances.
An iconic match-winning drop goal against Italy in 2014 and selection for the 2015 Rugby World Cup are just two of his highlights from the international stage, his club form for Worcester also earning him a recall to the squad ahead of the inaugural Autumn Nations Cup.
"It's massively exciting for me to be coming back to Glasgow Warriors," Weir told glasgowwarriors.org.
"Glasgow is my home and Glasgow Warriors is my boyhood club where it all began. It's always a massive honour pulling on the jersey and I'm really looking forward to doing it again.
"I've had some great chats with Danny. I'm excited to play a part in Glasgow's future and helping drive the club on to winning more silverware and competing at the top end of the table which we are both hugely passionate about.
"For my family it's going to be amazing just to being so close to home and the thought of my children growing up in Glasgow was hugely appealing to us when we were weighing up our options.
"I can't wait to get back out in front of the crowds at Scotstoun. You can't beat the atmosphere of a game under the Friday night lights."
Glasgow Warriors Head Coach Danny Wilson added: "Duncan is an experienced solid international ten who will give us a strong game management and goal kicking platform.
"He's Glasgow born and bred and someone who we believe will fit seamlessly back into our squad.
"Duncan knows exactly what it means to be a Warrior and is passionate about coming home.
"His experience will be a real asset to the squad next season - not only will he be a proven top-class operator available for selection, but he'll be someone that our young backs can work with and learn from."