- September 1, 1958 (First time it is made clear that Snoopy is Charlie Brown's dog)
- September 2, 1958 (It is confirmed that Linus is five years old in this strip)
- September 3, 1958
- September 4, 1958
- September 5, 1958
- September 6, 1958
- September 7, 1958 (This strip is adapted in Play It Again, Charlie Brown and A Charlie Brown Celebration)
- September 8, 1958
- September 9, 1958 (This strip is adapted in Good Grief, Charlie Brown: Peanuts, with Lucy replacing Violet)
- September 10, 1958
- September 11, 1958
- September 12, 1958
- September 13, 1958
- September 14, 1958
- September 15, 1958 (This strip is adapted in I Want a Dog for Christmas, Charlie Brown)
- September 16, 1958
- September 17, 1958
- September 18, 1958
- September 19, 1958 (This strip is adapted in Race for Your Life, Charlie Brown)
- September 20, 1958 (This strip is adapted in It Was a Short Summer, Charlie Brown)
- September 21, 1958 (Football gag for 1958, first time Charlie Brown yells, "Aaugh!" when Lucy pulls the football away)
- September 22, 1958
- September 23, 1958
- September 24, 1958
- September 25, 1958
- September 26, 1958
- September 27, 1958
- September 28, 1958
- September 29, 1958
- September 30, 1958