The Glasgow Warriors centurion will specialise in attack and the contact area under Head Coach Gregor Townsend, having previously worked with the Scotland setup during both the Guinness Six Nations and Rugby World Cup in 2023.
Horne moves to Scottish Gas Murrayfield on a full-time basis after a successful spell as part of Franco Smith's coaching team at Scotstoun, helping the squad to a first-ever European final and the top four of the BKT United Rugby Championship in 2022/23.
The Howe of Fife RFC product had previously spent 12 years as a player with the Warriors, amassing 446 points in 182 matches and becoming the most-capped back in Glasgow Warriors history.
The 34-year-old also earned 45 caps for Scotland during a decorated playing career, representing his country at both the 2015 and 2019 Rugby World Cups.
"My time coaching with Glasgow Warriors, as well as Ayrshire Bulls, has helped me prepare for my experiences with the national team and I have taken a lot of learnings from the past year," said Horne following his appointment.
"Coaching the Scotland team in the last year has been a privilege and a massive opportunity for me to work on the biggest stage. To have the chance to continue that in a full-time capacity is something I'm relishing.
"Working with this talented group of players greatly motivates me as a coach, as does the potential of this squad.
"I can't wait to meet up with the players and management in 2024 and make further progress."