In the cold open, Lucy encourages Charlie Brown to try and kick her football to honor the tradition of Thanksgiving football, then as usual pulls the ball away just before Charlie Brown reaches it and tells him that some traditions fade away.

As the Brown siblings prepare to go to their grandmother's for Thanksgiving dinner, Charlie Brown gets a phone call from Peppermint Patty, whose father is out of town so she invites herself — and soon after, Marcie and Franklin — to the Browns' house for Thanksgiving, even though Charlie Brown is not having dinner there nor can he cook anything beyond "maybe toast." Linus suggests that they prepare a Thanksgiving dinner for their friends before the Browns go to their own family meal and recruits Snoopy and Woodstock to help; Snoopy sets up a ping pong table and chairs outside. Charlie Brown, Snoopy, Woodstock and Linus then prepare a feast of toast, pan-fried popcorn, pretzel sticks, jelly beans and sundaes.

After Peppermint Patty, Marcie and Franklin arrive, Linus leads the group in a prayer that details the First Thanksgiving before Snoopy serves the meal. Peppermint Patty, who expected turkey and other traditional Thanksgiving food, angrily yells at Charlie Brown, who leaves the table dejected. Marcie suggests Peppermint Patty was too hard on Charlie Brown and asks whether he invited her or she just invited herself. Peppermint Patty, realizing she was in the wrong, asks Marcie to apologize to Charlie Brown on her behalf (unintentionally paralleling The Courtship of Miles Standish). Marcie reluctantly agrees, but Peppermint Patty soon follows and apologizes directly. Realizing that he and Sally are late for the Brown family dinner, Charlie Brown explains the situation over the phone to his grandmother, who invites all his friends to come along for dinner. On the drive over, they sing "Over the River and Through the Wood", but as they finish the song, Charlie Brown says there's one problem with that song: His grandmother lives in a condominium, not a house.

Snoopy and Woodstock go to Snoopy's doghouse and cook their own traditional Thanksgiving meal. They break the wishbone, with Woodstock receiving the larger piece. Over the end credits, the two eat pumpkin pie.

• Todd Barbee as Charlie Brown
• Robin Kohn as Lucy van Pelt
• Stephen Shea as Linus van Pelt
• Hilary Momberger as Sally Brown
• Christopher DeFaria as Peppermint Patty
• Jimmy Ahrens as Marcie
• Robin Reed as Franklin
• Bill Melendez as Snoopy and Woodstock
This is the last TV special that uses the same cast from Snoopy Come Home, You're Not Elected, Charlie Brown, and There's No Time for Love, Charlie Brown. In the next television special, Kohn, DeFaria, and Momberger would be succeeded in their respective roles by Melanie Kohn (Robin's younger sister), Donna Forman, and Lynn Mortensen, respectively.

The soundtrack for A Charlie Brown Thanksgiving was composed by Vince Guaraldi (except where noted) and conducted and arranged by John Scott Trotter. The score was performed by the Vince Guaraldi Quintet on August 20, 22 and September 4, 1973, at Wally Heider Studios, featuring Tom Harrell (trumpet), Chuck Bennett (trombone), Seward McCain (electric bass) and Mike Clark (drums).

Beginning in 1998, separate music cues have been released, scattered across several compilation albums:
• "Charlie Brown Blues" (version 1) and a composite edit of "Thanksgiving Theme" (consisting of versions 2 and 3) appeared on Charlie Brown's Holiday Hits (1998).
• "Linus and Lucy" (with the band) was released on The Charlie Brown Suite & Other Favorites (2003).
• "Little Birdie" and "Thanksgiving Theme" (version 3, with brass) appeared on Vince Guaraldi and the Lost Cues from the Charlie Brown Television Specials (2007) while "Is It James or Charlie?" (version 1) appeared on Vince Guaraldi and the Lost Cues from the Charlie Brown Television Specials, Volume 2 (2008).
• "Peppermint Patty" (edited version) and "Is It James or Charlie?" (version 2) appeared on Peanuts Portraits (2010).
On October 20, 2023, a full album containing the remastered original recordings for the special and several bonus tracks was released for the first time in honor of the special’s 50th anniversary.