The Scotland Under-19 international, who has made nine first-team appearances this season, has signed a deal that will keep him at Pittrodie until the summer of 2017.
Smith joins Jamie Langfield, Jonny Hayes and Peter Pawlett who also recently signed new deals with the club.
Aberdeen boss Derek McInnes is also hoping to persuade Reading to allow defender Michael Hector to return to Pittodrie when his current loan ends in January.
McInnes told the club's website: "I'm thrilled another player has committed his future with the club for three years. I'm really looking forward to playing a part in Cammy's development.
"This is a strong statement from the club, particularly with Jamie, Jonny and Peter also recently signing extended deals with Aberdeen.
"This is another important part of the jigsaw as we build for the future and Cammy will be a very important player within that."
Smith added: "As a local boy and an Aberdeen fan it was an easy decision for me to agree a new deal with the club.
"I have really enjoyed working with the manager and Tony (Docherty) since their arrival and I have no doubt they will play a huge part in my development as a player.
"I am excited about what Derek and Tony are looking to build here and hope I can really challenge to be part of their squad over the next few seasons."