The metaseries introduces Usagi Tsukino as a schoolgirl living in 20th-century Tokyo. She is initially depicted as a well-intentioned but underachieving crybaby who prefers the life of a normal teenage Earth girl. Nevertheless, she continues to fight the evils of her past life and protects the Earth with the Silver Crystal, as the Champion of Justice, Sailor Moon, which provides for most of the conflict within both the manga and the anime.

Her journey begins when, while running to school, she sees some neighborhood kids abusing a cat and rescues it (in the manga she accidentally steps on the cat). Later, the cat comes into her room and reveals herself as a talking cat named Luna, who serves as the mentor for the Sailor Moon. Luna gives Usagi a magical brooch which helps her transform into Sailor Moon (the "soldier for love and justice"), and tells her that she is a Soldier who must fight for peace. She also tells her that she must find the rest of the Soldiers, as well as their princess. Though at first Usagi is portrayed as a "reluctant heroine" (in the anime she often is rescued by Tuxedo Mask) as time goes on her character grows more confident and mature. However, she still has her crybaby moments late into the metaseries.

Usagi lives in Azabu Jūban (a real district of Tokyo) with her mother Ikuko Tsukino, her father Kenji Tsukino, and her brother Shingo Tsukino. Usagi's family take their names from the real family members of the metaseries' creator, Naoko Takeuchi. Out of the Sailor Senshi, only Usagi and Minako Aino live in conventional nuclear families. Usagi is also the only one known to have a sibling.

Usagi does not perform well at school, and often seems unintelligent (especially in the anime), though the storyline generally attributes this to naïveté and laziness rather than to actual stupidity. This is because she spends her time eating, playing video games and reading comics (including RunRun, which published the Sailor V manga in real life) rather than studying. She is often portrayed as a character that is better at art than science, as with her inability to answer that apples fall from trees because of gravity.

Usagi has a boyfriend named Mamoru Chiba. Mamoru and Usagi's relationship forms an important part of Usagi's life, as well as of the series. The love they share helps Usagi make it through many challenges. Mamoru becomes Usagi's boyfriend after many trials, and they date for a long time during the series. Mamoru eventually proposes to Usagi, and they ultimately get married.

A number of connecting episodes at the end of the first series reveal one of the biggest secrets about Sailor Moon and she realizes that she is Princess Serenity (the "crown princess" of the Silver Millennium) reborn. In the second series, Usagi learns that she will give birth to a daughter (Chibi-usa) by her boyfriend and future husband. Usagi will also become a "sovereign of the Earth", known as Neo-Queen Serenity, by the 30th century.

The series shows how Usagi loves sweet foods and how easily they distract her. She loves cake so much that it is listed as her hobby in the manga, and her favorite subject is listed as Home Economics. She is also said to dislike carrots (although she eats them in the anime), and is terrible at both English and mathematics. In addition to being a genuine friend, Usagi is extremely good at brown nosing when it's needed and, of course, crying to get what she wants. She is afraid of dentists and ghosts, and her greatest dream is to be a bride. Usagi loves rabbits as well as the colors white and pink, and is apparently a member of the Manga Drawing Club at school, though her skill level varies widely when shown in the anime. She stands 150 centimeters (4 ft 11 in) tall.

In the manga and anime, Mamoru gives Usagi the nickname "Odango" (a kind of rice dumpling), based on her distinctive hair-style. At first this is always accompanied with the suffix "-atama," meaning "head," but as time goes on it is left off. Usagi hates the name at first, but as they become close it develops into a sign of affection. Later in the series, other important male (or androgynous) figures in her life, Haruka and Seiya, adopt the name as well. Because there is no North American equivalent to odango, the English dub almost always uses "Meatball Head," once "Donut Head," and, somewhat incongruously, "Moon Face." In the English manga, Mamoru calls Usagi "buns", which is both an approximation of odango and short for Bunny.

Special powers and items Usagi is not shown using any special powers in her civilian form. She must first transform into a Sailor Senshi by wearing a special device (usually a brooch) and shouting a special command, which activates the device. Her original transformation command is "Moon Prism Power, Make-up!" She gains a new basic transformation sequence for each of the five major story arcs. In her basic form, the command changes as she becomes more powerful and obtains new transformation devices, evoking "Moon Crystal Power" and later "Moon Cosmic Power". A transformation into Super Sailor Moon initially requires her to already be in Senshi form and to use an additional item (called the Holy Chalice/Rainbow Moon Cálice) as well as the command "Crisis, make-up!", but in the anime this saps her strength. For the fourth story arc she gains the ability to transform directly into Super Sailor Moon via Moon Crisis, and in the fifth arc becomes Eternal Sailor Moon with Silver Moon Crystal Power in the manga, or Moon Eternal in the anime (and once in the manga). Most of Sailor Moon's anime transformations involve the use of shiny red or pink ribbons which come out of her brooch and form her uniform. Feathers and wings also figure prominently in some sequences, particularly the transformation into Eternal Sailor Moon. When her detransformation is shown, ribbons reappear and unravel from around her body and go back into the brooch. Usually the clothes she was wearing before she transformed reappear, but if her detransformation is forced, she may be left naked with the ribbons hanging loose around her body. She also has the Disguise Pen, which allows her to take on a human disguise by saying "Moon Power!" This is used very frequently in the first story arc, but is only mentioned once during the third arc.

As the protagonist and leader, Sailor Moon has the most special powers of any character in the series. Her physical attacks, usually one-offs and not always successful, include Sailor Moon Kick and Sailor Body Attack, as well as the occasional use of her hair pins as projectile weapons. In her very first battle, she cries in terror and the red hair pieces on her odango amplify the sound waves, doing damage to the enemy. Her odango ornaments can also be used to hear faraway sounds, although this is rarely ever used.

General magic attacks are her most common type of power. In each adaptation of the series she can remove her tiara and turn it into a throwing weapon, which is her first major attack and which she continues to use on occasion far into the anime series. In the anime she demonstrates the ability to control the path of her Tiara, and once, to enlarge it and then shrink it around the enemy, ensnaring them. In the manga, a powered-up tiara enables her to attack with Moon Twilight Flash while in the live-action series this move requires an item called the Moon Stick and is her primary attack, though she also sometimes uses unnamed beam attacks. In the manga and anime she only uses the Moon Stick to perform Moon Healing Escalation and return possessed humans to their normal selves; Luna says in the anime that this item belongs to the leader of the Sailor Senshi. In the anime, she once uses her tiara to purify a group of possessed people, and in the live-action series she can heal others without any incantation.

One cannot always distinguish between healing or purifying powers and attacks, as the monsters of the day in the series are usually created by corruption of an object or person. Sailor Moon has one or two primary attacks per story arc, most of which require a unique rod or wand, and in the original anime, each of them causes the target monster to shout a phrase and revert back to what it was made from (or to dust). These primary attacks are: the first series' Moon Healing Escalation, the second series' Moon Princess Halation, the third series' Moon Spiral Heart Attack and Rainbow Moon Heart Ache, the fourth series' Moon Gorgeous Meditation, and the fifth series' Starlight Honeymoon Therapy Kiss and Silver Moon Crystal Power Kiss.

A handful of powers come up only once and in critical situations; often the common repeating powers in the anime are only one-offs in the manga. In the anime, Sailor Moon uses her transformation command when battling Queen Metaria and when turning the Ayakashi Sisters into normal women. She says Moon Cosmic Power when struggling to destroy Pharaoh 90, and at the end of the series uses Silver Moon Crystal Eternal Power to fight Chaos.

Sailor Moon can be temporarily powered-up by the other Sailor Senshi lending her their powers, as shown in the climax of the Sailor Moon R movie and multiple times throughout the series. She also often attacks in tandem with her future daughter, Sailor Chibi Moon, and, at critical moments, receives power from individuals such as Luna, Queen Serenity, her future self, Mamoru, ChibiChibi, and others.

By far, Sailor Moon's most important item is the Silver Crystal, which is the "holy stone" of the Silver Millennium. It figures significantly in the first, second, and fifth story arcs, as it is the proof of her identity as the Princess and the source of her power. It eventually evolves into the Silver Moon Crystal.