Geraghty angered Exiles coach Toby Booth when he decided to leave London Irish for Northampton.
The 25-year-old had graduated from the London Irish academy and Booth said the club were "not prepared to be held over a barrel in terms of financial demands".
London Irish director of rugby Brian Smith insists Geraghty will be welcomed back to the club.
And the former England attack coach is excited by the prospect of Geraghty playing outside Ireland international scrum-half Tomas O'Leary, who is joining the club from Munster in the summer.
"I know Shane well and he is an exceptional player with a great deal of skill," said Smith, who also returned to the club this year.
"He's a game-breaking ball player and he's matured as a game controller. As we're a team that wants to attack, Shane is a great player to partner Tomas O'Leary.
"His contribution during his first spell with London Irish was massive and I know he will contribute the same when he joins us again.
"We're looking forward to welcoming him back into the fold."
Geraghty won all of his six England caps while at London Irish, for whom he scored 219 points in 71 first team appearances before leaving for Franklin's Gardens.
Booth felt let down by Geraghty's decision. He said at the time: "It's always disappointing when a homegrown player decides to leave for non-playing reasons given the resources the club has invested in developing him."
Geraghty failed to nail down a regular place in the Northampton starting line-up and he moved to Brive last summer, where he has helped the Top 14 club into the Amlin Challenge Cup semi-finals.
London Irish are rebuilding their squad for next season, with O'Leary and Leicester lock George Skivington having already signed up.
England internationals Delon Armitage, Nick Kennedy, Shontayne Hape and Paul Hodgson are all leaving the Exiles in the summer.
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