The experienced striker will join the Dons from Livingston at the start of June, having signed a two-year deal.
Affectionately known as JET, the 30-year-old has signed a two-year deal and joins Scott Brown and Declan Gallagher in committing their future to the club as part of Stephen Glass’ squad revamp.
The former Dons player, who replaced Derek McInnes, has promised further attacking recruits.
“We’re pleased to add Jay to our squad,” Glass said. “His arrival is a sign of intent and marks the first piece of the jigsaw as we look to re-build our front line.
“He brings a lot of attacking flexibility and can play in numerous positions as we look to add firepower to the group we have here.
“We’re working diligently behind the scenes and assessing players who fit the profile we are looking for here at Aberdeen
“It is imperative we take this opportunity to add the necessary quality of players and I look forward to enhancing our attacking options in the coming weeks.”
Emmnauel-Thomas proved himself a handful in games against Aberdeen for Livingston.
He scored nine goals in 31 appearances for the Lions.
“It feels great to be an Aberdeen player,” JET said, “Within football, Aberdeen has always had a very good reputation and to be involved with such a big Club is a great feeling.
“Based on games I’ve played against Aberdeen, watching the style of play, what the set-up is like behind the scenes and knowing where the manager wants to take the Club, of course it was something I wanted to be part of.”