- September 1, 1971
- September 2, 1971 (Snoopy appears as the World Famous Football Coach)
- September 3, 1971
- September 4, 1971
- September 5, 1971 (The third reference to Amy)
- September 6, 1971
- September 7, 1971 (This strip is adapted in There's No Time for Love, Charlie Brown and A Charlie Brown Celebration)
- September 8, 1971
- September 9, 1971 (This strip is adapted in A Charlie Brown Celebration)
- September 10, 1971 (This strip is adapted in It's the Easter Beagle, Charlie Brown)
- September 11, 1971 (This strip is adapted in Snoopy, Come Home and the segment "Football" from The Charlie Brown and Snoopy Show episode "Chaos in the Classroom")
- September 12, 1971 (The second reference to Citizen Kane in Peanuts)
- September 13, 1971 (Start of a storyline adapted in the title segment of The Charlie Brown and Snoopy Show episode "Lucy Loves Schroeder")
- September 14, 1971
- September 15, 1971
- September 16, 1971
- September 17, 1971 (End of a storyline adapted in the title segment of The Charlie Brown and Snoopy Show episode "Lucy Loves Schroeder")
- September 18, 1971
- September 19, 1971
- September 20, 1971
- September 21, 1971
- September 22, 1971
- September 23, 1971
- September 24, 1971
- September 25, 1971 (This strip is adapted in Snoopy, Come Home and the segment "Football" from The Charlie Brown and Snoopy Show episode "Chaos in the Classroom")
- September 26, 1971 (Football gag for 1971)
- September 27, 1971
- September 28, 1971
- September 29, 1971
- September 30, 1971 (The first full month of Peanuts without Marcie appearing)
| ← August 1971 | October 1971 → |