The pair have enjoyed a hugely successful relationship at the club where Edwards will remain head coach next season, winning the Powergen Cup, Heineken Cup and Guinness Premiership in successive seasons prior to the start of the 2007/08 campaign.
"I consider it an honour and a privilege to have worked with Ian McGeechan over the last few years," said Edwards, who aims to help McGeechan deliver yet another series victory with the Lions in South Africa next month.
"He is a friend, not only a colleague.
"Lots of people said we couldn't continue the success we had had under Warren Gatland, which always proved as a motivation force for people at the Club.
"That was proven wrong through three trophies in four years, including a Heineken Cup and Guinness Premiership title.
"I wish Ian all the best and he will continue to be both a friend and mentor to myself."