Buster Baxter is the best friend of Arthur Read and the deuteragonist of Arthur, and the titular protagonist of its spin-off, Postcards from Buster.
He is voiced by Daniel Brochu.
Buster wears a cyan polo shirt with a pink collar, blue jeans, orange boxer shorts with a UFO design (white briefs in the books), and red and white sneakers on his feet.
Buster is easygoing, fun-loving, and somewhat odd.
- Bitzi Baxter: Buster and his mother get along well, and his mother cares dearly for him (for example, in "Arthur Makes the Team", she asks Oliver Frensky if the baseball is hard, and if the cap is made of wool because he's allergic to it.
- Bo Baxter: Even though Bitzi and Bo are divorced, Buster sees his dad often. Buster and Bo travel together throughout the world.
- Grandmother-She is Buster's grandmother and the mother of Bitzi and Stu. She lives in the same apartment as her daughter and grandson. She loves her grandson very much.
Buster tends to stick with people in his class to be his friends, but he did make friends with Irwin and Sanjeev in "Home Sweet Home" while they shared a bunk at Camp Meadowcroak.
- Arthur Read: He is the best friend of Arthur and they share some interests, like Bionic Bunny, but Arthur thinks his food collection is nasty and UFO's do not exist.
- The Brain: He is another one of Buster's friends, despite the fact that whenever he thinks something was caused by aliens he attempts to try to prove him wrong (which has always been successful.)
- Francine Frensky: Despite Francine being mean sometimes, they have been friends for a long time and still are today.
- George Lundgren: During "George Blows His Top" Buster is shown to constantly ask George to borrow something of his. After borrowing George's tape recorder Buster comes across a recording of George explaining how he feels about being taken advantage of and then Buster comes and returns George's stuff and apologizes and explains if he knew he was hurting George's feelings he wouldn't have been doing what he was doing asking to borrow his stuff all the time. Buster then explains to George to try to be more honest with him because it'll save both of them a lot of trouble.
- Binky Barnes: Even thought there weren't friends in early episodes in later ones they are good friends. One time Buster was even afraid of Binky.