Aucoin is currently in the minors with the Hershey Bears, leading the AHL in scoring with 84 points - 31 goals and 53 assists.
He helped lead Hershey to the AHL championship last season.
The 5-foot-9, 162-pound Aucoin has three goals and eight assists in 21 games for the Capitals the last two seasons. He has played in nine games for Washington this season.
The extension was announced by the Capitals before their game against the Dallas Stars on Monday night.