- December 1, 1989
- December 2, 1989
- December 3, 1989 (This strip is adapted in the episode "Winter Wonderland" and "Too Cold" from the 2014 French TV series Peanuts. Snoopy replaces Linus. This strip was reprinted on December 14, 1997)
- December 4, 1989
- December 5, 1989
- December 6, 1989
- December 7, 1989
- December 8, 1989
- December 9, 1989 (This strip was reprinted on December 23, 1997)
- December 10, 1989
- December 11, 1989
- December 12, 1989
- December 13, 1989 (This strip was reprinted on December 22, 1997.)
- December 14, 1989
- December 15, 1989 (This strip is adapted in the episode "School Tomorrow" from the 2014 French TV series Peanuts and used on the page for August 4 of the Dayspring Peanuts A Year's Worth of Smiles and Blessings Desk Calendar)
- December 16, 1989
- December 17, 1989
- December 18, 1989 (Snoopy first appears as Santa Claus. This strip was reprinted on December 2, 1997)
- December 19, 1989 (This strip is adapted in It's Christmastime Again, Charlie Brown)
- December 20, 1989
- December 21, 1989 (This strip and the following two strips are adapted in It's Christmastime Again, Charlie Brown. This strip was reprinted on December 17, 1997)
- December 22, 1989 (This strip was reprinted on December 18, 1997)
- December 23, 1989 (This strip was reprinted on December 19, 1997. This marks a rare instance where Snoopy is apparently shown speaking out loud.)
- December 24, 1989
- December 25, 1989
- December 26, 1989
- December 27, 1989
- December 28, 1989
- December 29, 1989 (This strip is used on the page for December 31 [New Year's Eve] of the Dayspring Peanuts A Year's Worth of Smiles and Blessings Desk Calendar)
- December 30, 1989
- December 31, 1989
| ← November 1989 | January 1990 → |