Brill was released by Caley Thistle in the summer shortly after recovering from a knee injury which kept him out of action for more than a year.
And the former Luton player has remained in Scotland to challenge Craig Samson for a place in the Motherwell first team.
Brill told the club’s official website: “I’ve been working hard in the gym and it’s been a long comeback, but I feel that I’m now stronger and I’ve got that hunger to get back to where I was and hopefully go beyond that.
“I don’t think I ever lost (that hunger). I’m a football person: I love it, I love watching it and I’m football mad, so it’s nice now that the reigns are off and the injury is clear and I’m going to get a good pre-season under my belt and it’s a great opportunity at a club like this.”
Brill trained in Motherwell’s first pre-season session along with left-back Steven Hammell, who is yet to sign a contract extension.
Forward Scott McDonald’s future remains uncertain after being offered reduced wages to trigger the one-year option on his contract, while Stephen Pearson is expected to complete a return to Indian football despite having a year left on his deal.