O'Connor made his Super Rugby debut with the Force as a 17-year-old in 2008, which made him the youngest debutant in the competition's history at the time.
The versatile back played 39 Super games for the Force, scoring 10 tries across four seasons from 2008 to 2011, and to this day he remains the club's second highest points scorer.
More than 18 years on from his 2008 debut, the now 36-year-old will be back in Force blue, returning to Super Rugby ranks after one season in England's Premiership with Leicester.
"I'm so excited to join the Force. It feels like a full circle moment in my life," O'Connor said.
"Perth and the Force is where it all began for me as a 17-year-old, so this feels almost fated to find myself back here at this stage in my career.
"I've got a lot of love for Perth as a city. It's where we want to lay some roots down.
"We will welcome our first son into the world in a month or so, so it's a very special time for us."
O'Connor has featured in two World Cups, with the most recent of his 74 caps for the Wallabies coming against Ireland last November.
The veteran flyhalf hasn't given up hope of earning another Wallabies jersey, and next year's home World Cup serves as a major motivation.
But O'Connor knows he'll need a strong campaign for the Force next season if he is to turn his dreams into reality.
"I'm excited to come over and hit the ground running. I feel like my body is primed and my mind is ready," O'Connor said.
"I've had a great break now after going two years straight from the Crusaders to Wallabies and then Leicester.
"There's a lot of good footy still left in me. I want to make the most of possibly my last year.
"It's an incredible time in Australian rugby right now with the World Cup just around the corner, and this is an opportunity for me to go toe to toe with the best in Australia each week."
O'Connor, who has played 127 Super Rugby games across stints with the Force (2008-11), Rebels (2012-13), Reds (2015, 2019-24) and Crusaders (2025), is set to transition immediately into coaching once his playing career ends.
"James and I have spoken for the last three years about a return to the Western Force, but for various reasons the timing never quite aligned, despite a strong mutual desire to make it happen," Force coach Simon Cron said.
"Following our end-of-season review and evaluating our squad structure, the timing is now ideal.
"With our current group of playmakers - notably Ben Donaldson, Harry McLaughlin-Phillips, and Alex Harford - James provides an invaluable sounding board.
"Both Harry and Ben actively discussed the benefits of bringing him into the environment, which speaks volumes about our culture of peer-to-peer leadership and driving squad standards."
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