Horne, at the Borders side for the 2009-10 season, has been appointed as head coach of Fosroc Super6 side Ayrshire Bulls, winners of this season’s play-off final against Melrose-based Southern Knights in Edinburgh in October.
The 32-year-old replaces former Glasgow Warriors team-mate Pat McArthur at the South Ayrshire side next month, having acted as his assistant since last year and replacement in waiting pending the end of his playing days.
Horne, capped 45 times for Scotland since making his international debut in 2013, has been at Glasgow Warriors since 2009, featuring in 182 games to date, the all-time fourth-highest tally of appearances for the club.
Together with younger brother George, 26, Horne holds the record for most matches siblings have scored in, the pair having touched down in the same match on five occasions, including the 2019 Guinness Pro14 semi-final victory over Ulster and, most recently, against Benetton in January 2020.
“I feel incredibly fortunate to be retiring on my own terms after a career with both Glasgow and Scotland that I’m immensely proud of,” he said.
“Having spent many years playing under some of the very best coaches in the game, I have been inspired to follow in their footsteps and make the move into coaching myself.
“I know I’m so very lucky to have experienced all that I have, and to have done so playing alongside my childhood best friend and my little brother has been a dream come true.
“I have relished every moment of my 13 years and look back on them with only the happiest of memories and great pride.
“Thank you to all who have supported me on my journey so far. I will forever be grateful to each and every one of you. Here’s to the next chapter.”
Ayr club president Stewart Kerr said: “We are delighted to see Peter move into the head coaching role with the Bulls after impressing over the past year under Pat MacArthur.
“He brings a wealth of playing and coaching experience with him and we are positive for what the future has in store.
“Be it Ayr or the Bulls, we have built a reputation on success, and I have no doubt that more will follow in the coming seasons.”
Warriors managing director Al Kellock said: “Pete’s journey through rugby has been an inspirational one. From winning the schools cup with Bell Baxter and his time at Howe of Fife to all of the memorable moments he’s had in both a Glasgow and a Scotland shirt, his standards have never wavered from wanting to be the best.
“For any young kid growing up and wanting to play rugby, Pete is a perfect example of how to approach your rugby and how far you can go.
“He’s been a phenomenal team-mate and a phenomenal friend to so many at Glasgow Warriors.
“I’ve had the privilege of playing with him and also seeing the influence he has had on shaping the club as it is today.
“He’s a first-class professional who takes a huge amount of pride in making sure he is exactly where he needs to be.
“Pete undoubtedly has a tremendously bright future ahead of him, and we look forward to seeing how he develops as a coach at Ayrshire Bulls.
"He’s someone that will always remain close to the heart of this club.”
Warriors head coach Danny Wilson added: “Having made over 180 appearances for Glasgow in 12 years at the club and representing his country, Pete has achieved a huge amount in the game.
“He’s been a key part of our leadership group for a number of years and will be missed by all at the club.
“His attention to detail in his preparation both on and off the pitch is outstanding and recently his work mentoring our younger players and helping ensure the team taking the field are fully prepared has been fantastic.
“Pete has been a great servant to this club and we wish him, his wife Kirsten and their children all the best for the future.”