The centre has been out injured for the majority of the season but returned to action earlier this month as a replacement in the win over Benetton Treviso and also featured as a substitute in last weekend's win at Munster.
Horne will line-up at inside centre, with Mark Bennett coming in at out outside centre and Finn Russell moving to stand-off in place of Duncan Weir.
It's the same back three which started at Thomond Park last Saturday, with Peter Murchie at full-back and Tommy Seymour and Sean Maitland on either wing.
Chris Cusiter, who will once again captain the side at scrum-half, will form a new half-back pairing with 21-year-old Russell.
There are no changes to the pack from last weekend's win over Munster so Gordon Reid, Dougie Hall and Jon Welsh line up in the front row and Tim Swinson and Jonny Gray are in the engine room.
Josh Strauss, Chris Fusaro and Ryan Wilson continue in the back-row.
Glasgow Warriors head coach Gregor Townsend said: "Last week was a precious win for the club but we have another huge game in prospect at Scotstoun tomorrow night.
"Ulster are coming to Glasgow high on confidence and ahead of us in the league - so it's a very important game for both clubs.
"What impressed me most last weekend was our players workrate and how we kept taking the game to Munster. We'll need to repeat that effort again tomorrow.
"Our goal is to build on the win in Limerick and ensure we keep the momentum going over the next few weeks."
The capacity of Scotstoun has been increased to around 10,000 for the remainder of the season and tickets for Friday's game are available from glasgowwarriors.org or by phoning the ticket office on 0844 800 3490 (Monday to Friday, 9am-5pm).
The ticket office at Scotstoun will be open on Friday from 10.30am and tickets will be available right up until kick-off (subject to availability).
Glasgow Warriors team to play Ulster, RaboDirect PRO12, Scotstoun Stadium, Friday 18 April (kick-off 7.35pm) - live on BBC ALBA:
15. Peter Murchie
14. Sean Maitland
13. Mark Bennett
12. Peter Horne
11. Tommy Seymour
10. Finn Russell
9. Chris Cusiter (Captain)
1. Gordon Reid
2. Dougie Hall
3. Jon Welsh
4. Tim Swinson
5. Jonny Gray
6. Josh Strauss
7. Chris Fusaro
8. Ryan Wilson
Substitutes
16. Pat MacArthur
17. Ryan Grant
18. Geoff Cross
19. Leone Nakarawa
20. Rob Harley
21. Niko Matawalu
22. Ruaridh Jackson
23. Richie Vernon
Not available due to injury: Mike Cusack (medical/illness), Alex Dunbar (wrist/thumb), Stuart Hogg (hamstring), Ed Kalman (back), Sean Lamont (knee), Folau Niua (chest), Tom Ryder (knees), DTH van der Merwe (shoulder) and Jerry Yanuyanutawa (illness).
Guinness PRO12
Suite 208, Alexandra House,
The Sweepstakes
Ballsbridge, Dublin 4, Ireland