Martin Mystery is just like any other 16-year-old, and has a wild passion for the paranormal, but after un-willingly solving an "amazing out-of-this-world mystery," he finds himself working as a paranormal investigator for "The Center ." Whether at school or on a mission, he always remains the same outrageous immature teen, constantly bursting with energy. He seldom thinks before he leaps into danger, often to help someone in peril. He is an underachievier at school. Martin has a peculiar love for everything slimy, sloppy and gooey - things that make Diana gag. Martin loves to play pranks and creep out his stepsister, who often retaliates with physical or verbal abuse. He is also seen in Totally Spies saying that Sam is just like his sister which makes her mad. As the leader of the trio, Martin is also the only one who wears a U-Watch. Martin's favorite hobby is teasing Diana. A running gag in the series is Martin falling in love with every good-looking girl he meets, who usually reject him by using verbal or (in Jenni's case) phyiscial abuse . Voiced by Sam Vincent.
- In the episode "Lovespell From The Underworld", it is revealed that Martin has a diary. It also showed that Martin is left-handed.
- He studies at boarding school called "Torrington Academy".
- In the episode "Curse Of The Six-String Serenade", it showed that Martin can play guitar.
- He can play basketball and skateboard, as it showed in "Day Of The Shadows".Martin also said that his favourite snack was pickle ketchup chips.
- In the episode "It Came From Inside The Box" Martin said that he likes kids.