Die Serie handelt von den eineiigen Zwillingen Cody und Zack Martin, die mit ihrer alleinerziehenden Mutter Carey im Tipton Hotel wohnen. They overhear Dr. Olsen telling Nellie that it is a shame that Cody must lose his brain. Moved into The Tipton against their will, Cody and his brother Zack are forced to live with the bare minimum in a hotel suite while their mother sings in the lounge several nights a week. Cody moves up through middle school with his brother and they encounter several problems both there and at home, often with After a few days adjusting to sea life, Cody is forced to get a job in the episode "Broke 'N' Yo-Yo", where he becomes the ship's towel boy to earn money after Zack maxes out both of their student cash cards on non-essential items, particularly food and gifts for girls Zack was interested in.
Zack and Cody are confronted by Dr. Olsen, so they decide to make a run for it. At the internship, everything goes well until Zack follows Cody there. But Bailey, London, Woody, and Dr. Spalding rush in to stop Olsen. Cody is often shown wearing boxer shorts. Like brothers normally do, Zack and Cody often have arguments, however, they sport a typical brother-best-friend relationship from one another. Unfortunately, he is not accepted into Yale. This is revealed in "Computer Date". So London, Woody, and she head off to apologize to Cody. Cody Martin is one of the two protagonists in The Suite Life series, with the other being his brother, Zack Martin. Though Cody is shown to be quite sad about the loss of his relationship in the episodes following, it is not until "Twister: Part 2" that they finally get back together, admitting that they never stopped loving each other. Though he expresses a wish to be the first doctor-lawyer in space in "First Day of High School", this is never elaborated on further in the series. Though it takes them much thought, they eventually decide to participate and land themselves among dozens of other twins. He is generally nice to his older sibling but has the occasional time where he would rather be mean, taking after Zack's insensitivity somewhat. Carey ist dort als Sängerin angestellt und darf daher mit ihren Söhnen in dem 5-Sterne-Hotel in Boston, Massachusetts, leben.
In "Marriage 101", after a class project, Bailey discovers that she and Cody would not be able to be married happily.
The boys sneak into his lab to discover what the project is truly about. Dr. Olsen is still trying to merge the twins because he is extremely upset. After the disaster that took place in "Shipnotized", Cody decides that he no longer wishes to attend Harvard, and decides instead to go to Yale with Bailey. He had also won the election for 8th grade class president, as seen in the episode Like Zack, he inherited some musical talents from his parents. Cody tends to be more sensitive, caring and better behaved than his brother, but he is not perfect; he has a meaner and greedier side, portrayed in several episodes. Cody is more erudite, mature, and intelligent than his twin brother Zack. He is ultimately successful, and in "Wizards on Deck with Hannah Montana", the two finally begin dating. But as their week on the Gemini Project campus goes on, they soon discover that all is not what it seems. Cody wishes to win the Nobel Prize, and is shown to do so on multiple occasions when reflecting on his past in "Starship Tipton". In the spin off Cody holds on to the same general personality he had in the original series. After making the perfect plans to spend spring break with Bailey, Cody ditches the plans and goes off to work as an intern at a prestigious research firm, because he wants to be able to obtain a scholarship to Yale. Cody also learns that Bailey did make it into Yale, so they will now be miles apart.
He is the erudite, mature, and sensitive twin who gets straight "A"s (although he did avoid a "C" in wood shop by changing it to a pass/fail class).