|Arthur's Mystery Babysitter|
|Publication date||September 1, 2004|
|Published by||Little, Brown and Company|
| Preceded by|
Arthur's Jelly Beans
| Followed by|
Arthur's Off to School
Arthur's Mystery Babysitter is an 8x8 book, written and illustrated by Marc Brown. It was originally published on September 1, 2004.
Jane and David are preparing to go out, and Arthur asks who their babysitter will be. They answer that it will be a surprise, which Arthur and D.W. are worried about. D.W. reminds them about Kate, and David reassures her that the babysitter knows about Kate. Arthur and D.W. wonder who the babysitter is, from a pirate, a robot, an alien, or even Mr. Ratburn. When the doorbell rings, Arthur and D.W. hold their breath, but are happy to see that the babysitter is Grandma Thora. D.W. tells Thora that she is glad to see her, and Thora responds that she loves her and Arthur.