The 34-year-old former England Under-21 international has joined the Dons squad on a pre-season tour of Ireland after committing himself to half a season at Pittodrie.
Manager Derek McInnes told Aberdeen's official website: "I'm delighted to get Nicky on board.
"To get such an experienced and talented goalkeeper is important and to get him during the pre-season stage is great for him in terms of being able to integrate with the boys.
"We had a few avenues and other options but we feel with the signing of Nicky we've recruited well and Nicky's eagerness and willingness to come here was pivotal."
Sheffield-born Weaver played 172 league games for Manchester City and can also number Charlton, Dundee United and Burnley among his former clubs.
The experienced keeper offers McInnes an alternative to current number one Jamie Langfield and Irish teenager Danny Rogers in north east Scotland.