The 30-year-old joins from MLS franchise Houston Dynamo and will be handed the No.9 shirt at Pittodrie ahead of next season.
Ramirez put pen to paper on a two-year deal, becoming Stephen Glass’ seventh signing since becoming Dons boss.
The manager told Aberdeen’s website: “Securing a centre forward was vital for us and, when we started looking, Christian immediately became a priority.
“We have had to work really hard as a club to get this finalised and we are delighted to be able to add a proven goal scorer who is still at a good age and is a full internationalist.
“We have no doubt he is going to add great value to our team and help all the individuals within it.
“His professionalism has been known to us for years through his relationship with Allan and his footballing ability will be obvious to everyone. I am sure he will display the reasons why we pursued this deal so vigorously.”
Ramirez, who has two caps for his nation, stated his delight at moving to the Scottish Premiership side.
He said: “I feel extremely blessed and excited about the opportunity to play for such a historic club, and more importantly to be part of this new era under the manager, Stephen Glass.
“When the prospect of joining Aberdeen FC was presented to me, I knew it was one I couldn’t pass on. I can’t wait to get to Aberdeen and meet the staff, players and supporters. I’m ready to give this club my all.”