The Bristolian, 19, who has made one first-team appearance for the Robins after progressing through the club's academy, follows quickly in the footsteps of fellow graduate Joe Bryan in penning a new two-and-a-half-year deal.
Manager Derek McInnes said: "Bobby's a great boy to have about; a hard-working lad. He's similar in many ways to Joe Bryan, who signed a similar deal recently.
"He does everything right off the pitch in terms of his conditioning, and on the training pitch you can see he wants to make the best of what he's got.
"Bobby has two good feet, can see passes and is a confident lad. It's important we steer him in the right direction in terms of his education and development."
Reid has starred as an ever-present this season for the club's development squad in under-21 fixtures, scoring five goals in seven games.