Tommie Hoban has joined the Dons on a short-term deal until January 2021.
The defender has been training with Aberdeen to finish his rehab after was injured whilst playing for the Dons.
He had been out for a year since he injured his knee in our game against St Mirren.
Derek McInnes said on the signing: “I enjoyed working with Tommie prior to the injury he sustained in an Aberdeen shirt and following his rehab with us we’ve taken the option for him to join us whilst we are a defender short.
“I’m delighted to get a player of his quality and I regard him very highly, not only as a player, but also as a person. We are mindful he is a bit short of fitness, but he has put in a lot of hard work and I am assured we can get him up to speed quickly.”
The free agent was on loan from EPL side Watford at the time, but was released at the end of his contract last summer.
The former Republic of Ireland U21 international did his cruciate-ligament at Watford before returning to fitness and making way for the Dons.
Hoban was later sidelined with a shoulder problem and then he did his cruciate on the other knee.
Derek McInnes said: “Tommie was up with us before the season was curtailed and we just wanted to continue that really because we feel it is the right thing to do.
“It is good to have him back and he will be with the physios for the next week or so and hopefully he will start to make progress towards his rehabilitation.”
Tommie has been allocated shirt number 3 and will be in the squad to face Rangers tomorrow.