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