Yukiko Amagi is a rich and elegant young woman who is popular with boys and girls alike. At first, Yukiko is very introverted, but she gets livelier after she is rescued from the Midnight Channel. Often scoring the best during exams, she is intelligent and often repeats the material with her best friend Chie Satonaka. Despite being intelligent, she is prone to brainfarts and having moments of clumsiness. According to Kanji Tatsumi in his P4A story mode, Yukiko is also open-minded and straightforward. Yukiko is not only shown to be quite fearless and unflinching in the face of creepy atmospheres and surroundings, she also greatly enjoys horror stories, much to the dismay and chagrin of Chie, who is easily frightened upon the mention of such things. As a smart, attractive, feminine, respectful, polite and hard-working teenager, she has attracted many male characters in Inaba such as Mitsuo Kubo, but acts uncomfortably when someone mentions her beauty. .

She also truly appreciates and cares about her friends, as well as her parents and staff from the Inn, and often vows to become an even stronger, more dependable person so that one day she, in turn, will be able to support and protect them just like they have did to her in the past. She is also shown to take the well being of new friends she makes seriously, as in Persona 4 Arena when Yukiko solemnly promises to save Labrys from danger and protect her from harm just recently after bonding with her (albeit this was in her own story mode) and Persona Q where Yukiko assures Rei and Zen they'll be safe as long as she's around, going so far as to being a big sister figure to Rei when she bonds with her after Rei asks her if she can call Yukiko "Yuki-chan."

Chie's biggest insecurity is her femininity, which is one aspect of her unhealthy relationship with Yukiko in which both of them are secretly guilty of hiding their true feelings from one another. After years of being with Yukiko who is treated as wealthier, more popular, scoring higher grades in school and having more male admirers, Chie gradually develops an inferiority complex in comparing herself to Yukiko and is jealous of all the male attention Yukiko receives. Chie's brash personality seems to makes it hard for boys to approach her romantically despite the fact that some students, including sports captain Kou Ichijo, secretly find her attractive. As a result she comes to believe herself to be undesirable, especially compared to Yukiko. This causes her to derive satisfaction from Yukiko's need to rely on her for confidence and support at the beginning of the game.

Her biggest insecurity is being chained down. Her whole life she has felt she is on a railroad track with no opportunity for deviation. Yukiko views that her parents and family are forcing a lifestyle on her which she isn't even sure she wants. For example, they chose the name "Yukiko" for her, a name which she hated. They then expect her to inherit the Amagi Inn, an inn which she isn't sure she wants to inherit either, which requires a heavy workload and a lot of responsibility. Yukiko then develops a desire to run away from such life and start anew.

By the end of the game she has realized that in reality, she is perfectly comfortable with the way her life is progressing and she can control her life just as much as she desires to. She decides to inherit the inn, but this time, it is from her own choice, rather than an inherited expectation.

Throughout Persona 4, Yukiko has a few notable running gags. For example, one of them is that she tends to have very easy laughing fits from the slightest jokes, though there are later times where even Teddie of all people fails to make her embrace a joke. Another running gag is that she is practically an airhead at times and completely misreads situations (i.e. Golden fireworks night).

Also, like Fuuka and Chie, Yukiko is known to be a downright horrible cook. Yukiko's and Chie's cooking skills have become a recurring joke throughout the story. During the protagonist and Yosuke's first camping trip, the girls attempted to cook dinner, which ended horribly. Yosuke would continue to refer to the curry they cooked during the camping trip and all of their future cooking as "Mystery Food X." This is because that she often uses expensive but inappropriate ingredients in her cooking, causing them to lose their flavor. During the celebration of Mitsuo's arrest where the investigation team cooks omelets for Nanako, the one she made has no taste at all.

In Persona 4, it is shown that Yukiko doesn't appreciate sexual innuendo and vulgar jokes, and even will go so far as to slap those who make them, such as Yosuke and Kanji.