Vokoun spent only one season with the Capitals and is set to become an unrestricted free agent on July 1. He was signed last summer as one of several veterans pegged help the team win its first Stanley Cup.
The 35-year-old Vokoun finished with a record of 25-17-2 and a .917 save percentage in 48 games for Capitals. He has also played for Montreal, Nashville and Florida in his NHL career.
The trade was announced Monday.