From the distant past, the Outer Sailor Senshi were given the task of protecting the Silver Millennium from enemies who intrude from outside the solar system. On Earth, Sailor Uranus and Sailor Neptune become, respectively, Haruka Tenoh and Michiru Kaioh, partners and lovers a year older than the Inner Senshi. They work together for some time, only later joined by Setsuna Meioh (Sailor Pluto), a college student, and by Hotaru Tomoe (Sailor Saturn), a much younger girl (whose age varies due to rebirth and accelerated growth).
The Outer Senshi appear charming, mature, and personable in their civilian forms, and the Guardian Senshi admire them enormously. However, they often demonstrated extreme dedication to their roles as soldiers, and, should they determine that sacrifices need to be made, can be entirely ruthless with allies as well as enemies. In their Senshi forms, they were cold, aloof, and were not inclined to trust offers of help from the Guardian Senshi, preferring to work alone (although Pluto, perhaps because of her close relationship with Chibiusa, seemed a little more open to working with the Inner Senshi than Uranus and Neptune did and often acted as a 'mediator' between the two groups). In an episode of the anime, Mamoru, after having a conversation with the Outer Senshi, advised Usagi and her friends not to fight along with them, as "the world you wish for and what they wish for...is completely different", although at the end of the episode he changed his mind after seeing the Outer Senshi unable to defeat the Death Busters on their own.
Usagi's relationship also worsened with Haruka and Michiru, mainly due to her and ChibiUsa's strong criticisms against the Outer Senshi for their plans concerning Hotaru Tomoe. Things escalated further after the Death Busters were defeated as Haruka and Michiru begin making threats against Usagi, telling her to give up her position as future Queen of the Crystal Tokyo. This lead to a fight that broke out between them and Sailor Moon in which they were defeated. Afterwards, they knelt down, apologized and accepted Sailor Moon as their future Queen.
Each of the Outer Senshi fight with a special weapon; Uranus, Neptune, and Pluto bear the three Talismans, and Sailor Saturn carries the Silence Glaive. When first introduced, the Outer Senshi's powers were significantly stronger than those of the Guardian Senshi's, and as a result, the Outer Senshi rarely allowed the Guardian Senshi to interfere with their missions. By the time of the Stars arc, however, all of the Sailor Senshi, excluding Sailor Saturn, were granted new Crystal powers that were equal to one another, thus allowing them all to feel much more comfortable working together. Sailor Pluto is the strongest and the most powerful of all the Senshi. As the series progress, they also seem to develop psychic powers, able to sense and foretell impending dangers through nature and visions.
- The Outer Senshi's "Super Form" transformations are never shown in the anime.
- During their transformations in the anime, Sailors Neptune, Uranus and Pluto are all shown with makeup. This may be a reference to the fact that some cultures believe that make-up is only for mature girls; the Outer Senshi are usually depicted as more "grown-up" and have different beliefs similar to an adult's, thus make-up is added to enforce that idea.