The 34-year-old former England Under-21 international was a free agent after his contract with Sheffield Wednesday expired.
Sheffield-born Weaver played 172 league games for Manchester City and has also turned out for Charlton, Dundee United and Burnley.
Aberdeen manager Derek McInnes told RedWeb: "To get such an experienced and talented goalkeeper is important, I'm delighted to get Nicky on board.
"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."
The Dons support will hope that despite the half-year contract, Weaver will provide a genuine alternative to haphazard glovesman Jamie Langfield, unlike many previous keepers to have worn the jersey in recent years.