|Family||Liam (unknown close family relationship)|
|Book debut||Arthur's Eyes (book)|
|Cartoon debut||"Arthur's Eyes"|
|Voiced by||Walter Massey (s1-s18)|
Mr. Marco is one of the second-grade teachers at Lakewood, and was Arthur's teacher before he started learning under Mr. Ratburn. He is a kind teacher but doesn't tolerate any misbehavior from his students, and has zero-tolerance for cheating.
According to the episode, "Arthur and the True Francine", he once punished Francine for copying off Muffy's paper during a math test, although it was later discovered that it was Muffy who cheated by copying off of Francine, and she was punished instead.
Mr. Marco cares a lot about his students and does his best to give them a good education. He can be very stern if somebody cheats in class. Despite knowing Francine well, he suspects her rather than the new girl Muffy of cheating, simply because Muffy makes an elaborate denial.
The desks in his classroom are usually separate from each other in rows and facing the front of the classroom (unlike Mr. Ratburn whose classroom has groups of four desks that allowed the students' desks to face each other).
Mr. Marco dresses similar to Mr. Haney. He wears a light sky blue jacket with a yellow cream shirt underneath and a tie. He also has light sky blue pants and brown shoes. His coaching outfit is the same color but consists of only a sweater and darker athletic pants with a white ball cap. In the early Arthur books, he was depicted as a moose with glasses, but the cartoon changed his appearance into an aardvark and removed the glasses.
- Season 1
- Mr. Marco's most prominent appearances were in Season 1, but he has appeared very rarely since then.
- In "Arthur's Eyes", he has the same classroom as Mr. Ratburn, but in "Arthur and the True Francine" the walls of his classroom are purple and there are dinosaurs painted onto them.