The experienced striker, who has scored 4 goals in 25 appearances for Scotland, agreed a severance package from United who he joined in January after initially turning down the Dons. Crawford is believed to have fallen out with the United management, and became surplus to requirements with the addition of Lee Miller and David Fernandez to the Arabs' squad.
Crawford was locked in talks with both Aberdeen and former club Dunfermline late into Wednesday night before committing himself to a 2-year deal at Pittodrie, with the hitman due to join up with the Dons in the next couple of days.
The signing of Crawford ends weeks of searching for the elusive second striker to complete the Dons' summer signing spree. He becomes the sixth new addition to the squad, alongside Barry Nicholson, Steve Lovell, Jamie Smith, Gary Dempsey and Jamie Langfield.