Princess Peach's initial appearance was drawn by Shigeru Miyamoto. Miyamoto later asked Yōichi Kotabe to redraw Peach with his instructions. He had asked Kotabe to draw her eyes to be "a little cat-like" and that she should look "stubborn, but cute". With Kotabe's influence, Princess Peach changed considerably.

Princess Peach has long yellow-blonde hair, sky-blue eyes, a tall height, a slender but curvy figure, and a rosy complexion. Peach's make-up is black mascara and pink lipstick. She wears a pink dress, red high heels, white evening gloves, a sapphire brooch, sapphire earrings, and a gold crown with sapphires and rubies.

Peach's personality is generally kind natured and well mannered. In most games she is portrayed as selfless and generous. Typically, she does not show an aggressive nature even when she is fighting (this is done by quick slaps, elegant high kicks thrusts in the air, and other gracious fighting techniques (as seen in the Super Smash Bros series)) or confronting her enemies. This, however, varies slightly from game to game. One of Peach's most common traits during her playable appearances is her ability to temporarily float in the air with her large skirt, and later on, with her umbrella. This was first featured during Peach's first playable appearance in Super Mario Bros. 2. She was one of the more popular character choices in this game since her ability made navigating across platforms easier (though her own jumping was rather short). This ability has also appeared in Super Paper Mario and her playable appearances in the Super Smash Bros. series.

In Japan, the Princess's name has always been Peach (ピーチ姫, Pīchi Hime?, Princess Peach). She was originally known as Princess Toadstool in the United States and other Western countries. The English translation of Yoshi's Safari (1993) marked the first usage of the name "Peach" outside of Japan; however, the name did not catch on at that time, as the game itself was not very popular. In Super Mario RPG: Legend of the Seven Stars, she went back to being called Princess Toadstool. It was not until Super Mario 64 that the name Peach became widely known outside Japan.

In her first voiced appearance in the 1986 Japanese anime Super Mario Bros.: Peach-Hime Kyushutsu Dai Sakusen! (Super Mario Bros.: The Great Mission To Rescue Princess Peach) Peach was voiced by Mami Yamase, a pop singer. In the OVA trilogy released in 1989, she was voiced by Miyako Endo. On the cartoon segments on The Super Mario Bros. Super Show!, Peach was usually voiced by Jeannie Elias. In The Adventures of Super Mario Bros. 3 cartoon from DIC Entertainment, Princess Toadstool was voiced by Tracey Moore. In the CD-i game Hotel Mario, Peach was voiced by Jocelyn Benford. In Super Mario 64 and the English version of Mario Kart 64, Peach was voiced by Leslie Swan, a localization manager for Nintendo of America. Swan voiced Peach again for the release of Super Mario 64 DS in 2004 and in Super Paper Mario in 2007 In Mario Party, Mario Party 2 and the Japanese version of Mario Kart 64, Peach was voiced by Asako Kozuki. Starting with Mario Golf on the Nintendo 64, Peach has been voiced by Jen Taylor.

In 2005, Nintendo used a new voice for Princess Peach. Although Super Princess Peach and Mario Hoops 3-on-3 still used Taylor's voice, other games, such as Mario & Luigi: Partners in Time and Super Mario Strikers have a new Peach voice, Nicole Mills. The infant form of Princess Peach that appears in Mario and Luigi: Partners in Time, Yoshi's Island DS, Mario Kart Wii and Mario Super Sluggers, known as Baby Peach, is voiced by Mills, though replaced by Samantha Kelly starting with Mario Kart Wii. However, in Super Paper Mario, Peach is once again voiced by Swan. Peach has been voiced by Samantha Kelly since Mario Strikers Charged. In Mario & Sonic at the Olympic Games, Peach is again voiced by Taylor, although much is from sound clips recycled from previous Mario games. Likewise, if a player selects Peach in Brawl using a Wii Remote or classic controller, Peach's taunt from Melee (then voiced by Taylor) will sound over the Wii Remote's speaker if the volume is on.

Peach is portrayed as the princess of the Mushroom Kingdom, her birthplace and current residence. Within the castle are Royal Guards known as mushroom retainers. In Super Mario RPG: Legend of the Seven Stars and Paper Mario, a cabinet minister or chancellor is part of the Mushroom Kingdom government. Toadsworth, the steward of her castle is accidentally referred to as her grandfather. Her father, the Mushroom King, though implied, has never made an appearance in the games. Her mother in unknown. Peach also has a grandmother and a grandfather who is the Chancellor.

Peach first appeared in Super Mario Bros. and has been kidnapped by the series' main antagonist, Bowser, many times since. In Super Mario Bros. 2, Princess Peach was a playable character. Peach, along with Mario, Luigi and Toad were called by the inhabitants of Subcon to save their dream land from the evil Wart. Peach's main ability was that she could hover for a limited time after jumping left or right. This skill allows her to easily make jumps over areas larger than other characters could. In Super Mario Bros. 3, Bowser's children capture the seven Toadstool kings. Hearing of this, Princess Peach asked Mario and Luigi to rescue them, sending them items while they were on their quest and providing them with power-ups after completing each level. She is eventually captured herself and later saved by Mario. In Super Mario World, Mario, Luigi and Peach were having a vacation in Dinosaur Land when Bowser once again kidnapped her. This time, she was held captive in Bowser's castle in the Valley of Bowser. Bowser had brought her inside his Koopa Klown Kar for the battle against the brothers. In the end, Peach was rescued by Mario, and she gave him a kiss on the cheek.

In Super Mario RPG: Legend of the Seven Stars, Peach was one of Mario's party members, along with Mallow, Geno and Bowser. Peach possesses healing/resurrection powers similar to Mallow. In Super Mario 64, Peach invited Mario to her castle for a cake, but before Mario arrived at the castle, Bowser came and took control of the Power Stars. He kidnapped Peach in the fresco over the entrance of the castle. In Paper Mario, Peach invites Mario to her castle, but as soon as he meets with her, Bowser lifts her castle into the sky and throws Mario out a window. He has to collect star powers in order to defeat Bowser, save her, and return her castle to the Mushroom Kingdom. When lonely in her bedroom, she encounters a Star Kid named "Twink". She is a playable character in the scenes after Mario has rescued each of the seven Star Spirits, except one after Kalmar has been rescued. Her segments involve her sneaking past guards in order to gain intelligence that Twink can pass onto Mario. When she reads Bowser's diary, she learns that he actually has a crush on her.

In Super Mario Sunshine, Mario, Peach, Toadsworth and an entourage of Toads went to Isle Delfino on Peach's private plane. However, Bowser Jr., in the disguise of Shadow Mario, had filled the island with graffiti. The crimes were blamed on Mario, and he was sentenced to clean the entire island with FLUDD. Eventually, Bowser Jr. kidnapped Peach while Mario was away, and took her to Pinna Park, where he revealed his true identity. Bowser had told him that Peach was his mother and that the evil Mario had kidnapped her. After Mario destroyed Bowser Jr.'s Mecha-Bowser, in which the princess was held captive, Bowser Jr. used a balloon to take the still intact head of the Bowser robot to Corona Mountain, with Peach still inside. Later, Mario made his way to the top of the active volcano and found Peach and was forced to battle with Bowser and Bowser Jr. in a pool of green acid. This was described by Bowser as a "family vacation". Mario managed to rescue Peach, and later they were able to enjoy their vacation together with FLUDD. Bowser later admits that Peach is not Bowser Jr.'s real mother. Princess Peach was kidnapped once again in New Super Mario Bros. However, as in Super Mario Sunshine, the culprit was not Bowser but his son, Bowser Jr.