Emergency services were called to the site around 4.45pm.
Balfour Beatty is main contractor on the £18m project to build a 90 metre bridge over the River Don.
A Balfour Beatty spokesperson said: “Yesterday afternoon, a colleague working on the Third Don Crossing construction project in Aberdeen died.
“Our deepest sympathies are with our colleague’s family, friends and co-workers at this time.
“We are liaising with Police Scotland and the Health & Safety Executive to support their investigations and while these continue it would not be appropriate to comment further.”