Ross Bagdasarian, Jr.
Alvin / Simon / David Seville (voice)
Janice Karman
Theodore / Tommy's Sister (voice)
Frank Welker
Santa Claus / Doctor (voice)
Charles Berendt
Clyde Crashcup (voice)
R.J. Williams
Tommy Waterford (voice)
June Foray
Mrs. Waterford / Mrs. Claus