The Scotland international had a shoulder operation over the summer, but played 60 minutes for the Warriors 'A' team on Monday in their 30-5 win over Edinburgh Rugby and goes straight into tomorrow night's starting line-up.
After joining from Munster in the summer, Irish centre James Downey makes his full debut for the club in the No.12 shirt, while Tom Ryder and Finn Russell could make their first appearances of the season from the bench.
Following last Saturday's 33-13 win over the Dragons in Newport, Stuart Hogg continues at full-back and DTH van der Merwe keeps his place on the left wing, with Sean Lamont coming in for Tommy Seymour on the opposite side.
It's a new centre partnership with Downey linking up with Mark Bennett in midfield, while Duncan Weir continues at fly-half and Henry Pyrgos comes in at scrum-half.
The only change in the front-row sees Pat MacArthur taking over from Kevin Bryce at hooker, after recovering from a head knock, while Gordon Reid and Euan Murray continue at loose-head and tight-head respectively.
Kellock comes into the second-row in place of Leone Nakarawa and will partner Tim Swinson.
Chris Fusaro replaces the suspended Tyrone Holmes at open-side, while Adam Ashe takes over from Josh Strauss at Number 8 and Rob Harley continues on the blind-side.
More than 5,000 tickets have been sold for tomorrow night's non-televised game but standing tickets in the east terrace are still available priced at £15 for adults, £10 for students and £5 for under-18s in advance from www.glasgowwarriors.org.
Adult and concession tickets will increase by £5 on matchday and tickets will be available at the stadium from 12pm tomorrow (subject to availability).
Glasgow Warriors head coach Gregor Townsend said: "Connacht are one of the form teams in the league right now and had an impressive win against Leinster last weekend, which combined with their win away in Toulouse last season, shows the progress that they are making under Pat Lam.
"Tomorrow night's game is another big test for our squad, but one we're all looking forward to. It'll be good to be back home at Scotstoun, playing in front of our own supporters, after a couple of weeks on the road.
"We welcome Al Kellock, Tom Ryder and Finn Russell back from injury tomorrow night. They've all worked really hard to come back and it's great news that we can include them in our squad for this game."
Glasgow Warriors team to play Connacht, GUINNESS PRO12, Scotstoun Stadium, Friday 26 September (kick-off 7.35pm):
15. Stuart Hogg
14. Sean Lamont
13. Mark Bennett
12. James Downey
11. DTH van der Merwe
10. Duncan Weir
9. Henry Pyrgos
1. Gordon Reid
2. Pat MacArthur
3. Euan Murray
4. Tim Swinson
5. Al Kellock (Captain)
6. Rob Harley
7. Chris Fusaro
8. Adam Ashe
Replacements
16. Kevin Bryce
17. Jerry Yanuyanutawa
18. Rossouw de Klerk
19. Tom Ryder
20. James Eddie
21. Murray McConnell
22. Finn Russell
23. Tommy Seymour
Not available due to injury: Mike Cusack (medical/illness), Ryan Grant (shoulder), Jonny Gray (chest/ribs), Sean Maitland (quadriceps), Niko Matawalu (back), Leone Nakarawa (foot), Josh Strauss (quadriceps), Richie Vernon (achilles), Jon Welsh (shoulder) and Ryan Wilson (shoulder).
Guinness PRO12
Suite 208, Alexandra House,
The Sweepstakes
Ballsbridge, Dublin 4, Ireland