After saving a prince named Eric in the ocean from a burning ship, Ariel finds herself falling in love with him, and plans on meeting him once again at the Under the Sea celebration at Eric's kingdom, which is held to pay tribute to the sea goddess Ursula. Along the way, she saves a person named Snow White from drowning after she jumps off a cliff to escape Queen Regina's guards. After taking her shore, Ariel explains her plans to Snow, and reveals that every year when the high tide rises, Ursula grants merfolk the ability to walk on dry land until the next one occurs. Ariel gains human legs, and goes to the ball with Snow. She eventually gets the chance to meet up with Eric, who recognizes her as the person who saved him from the shipwreck, but Ariel denies this. The two dance together, and Eric falls in love with her, inviting Ariel to join him on an expedition to Agrabah. Ariel finds this as a dilemma, because she would have to make Eric choose between his dreams of exploring the realm or giving it all up for her. She mulls over this problem out loud in front of the ocean, summoning Ursula.
Ursula gives her a magic bracelet which will allow her to become human, permanently. However, someone else must take her place as a mermaid. Ariel chooses Snow White, after hearing Snow talk about her desire to escape the Evil Queen's clutches. After Ariel puts the bracelet on her, Snow White turns into a mermaid, just as Queen Regina arrives. Snow is unable to escape as she is not in the ocean, and she is nearly killed until Ariel attacks the Queen, stabbing her in the neck with a fork. Ariel takes the bracelet off of Snow White, and they both escape. Ariel is now a mermaid, but once she takes Snow to a safe place, Snow urges Ariel to return to Eric and tell him that she is a mermaid. Ariel eventually decides to return back to Eric's kingdom and sees Eric waiting for her. She then tries to call out his name, only to discover that the Evil Queen has stolen her voice. Desperate to find Eric, Ariel travels to Agrabah where she meets Princess Jasmine. Jasmine helps her locate Eric's camp, but find out the "Eric" that is in Agrabah is really a disguised Jafar, who sends Ariel back to the sea.
In Neverland, Ariel is summoned by Regina and Rumplestiltskin to travel to Storybrooke and collect Pandora's Box, so that they can trap Peter Pan. The Evil Queen gives her the bracelet in order to allow Ariel to turn into a human, and also returns her voice. Ariel arrives in Storybrooke, and manages to obtain Pandora's Box with the help of Belle. After giving Pandora's Box to the Evil Queen and Rumplestiltskin, she returns to Storybrooke in order to find Eric. Belle helps Ariel find Eric, and the two share a passionate kiss, as they are finally reunited.
When the second Dark Curse is unleashed, everyone is returned to the Enchanted Forest, where Eric is kidnapped by pirates. Ariel confronts Hook, but he hadn't kidnapped Eric and they discover who not only kidnapped the prince but also stole Hook's ship, the pirate Blackbeard. Hook defeats Blackbeard, but Ariel tells Hook not to kill him otherwise they'll never find out where Eric is. However, Hook makes Blackbeard walk the plank. Ariel slaps Hook, before transforming into her mermaid form and, without Hook's knowledge, saving Blackbeard. Using Blackbeard's information, Ariel eventually does find Eric on Hangman's Island, and the two live there together. When Snow White unleashes a third Dark Curse, it does not reach Ariel and Eric's island.
When Queen Elsa of Arendelle traps Blackbeard's ship in a bottle, Ariel happens to be swimming nearby and gets trapped in the bottle as well. Ursula summons the bottle to Storybrooke, and they manage to free the ship, freeing Ariel. After Ursula knocks Hook unconscious and throws him in the water, Ariel saves him and later thanks the pirate for freeing her, for now she can swim back to the Enchanted Forest to be with Eric again.
When Hook, Jasmine and Aladdin arrive at Hangman's Island, they come across Ariel, and discover that she has Jafar's genie bottle in her possession. When Jasmine releases Jafar, he knocks Ariel, Hook and Aladdin unconscious until Jasmine manages to defeat Jafar by using a magic powder to trap him in the form of a wooden staff. When Agrabah is restored, Ariel lets Hook use one of her magical seashells to communicate with Emma.
- Ariel is based on the mermaid in the fairytale, The Little Mermaid.
- At the Under the Sea celebration, she expresses interest in a fork, which later comes in useful in a confrontation with the Evil Queen. This is a reference to the 1989 Disney film, when Ariel collects a fork which is incorrectly identified as a 'dinglehopper'.
- Unlike most mermaids, Ariel is more friendly as opposed to the ones in Neverland.
- S3, E06: "Ariel"
- S3, E07: "Dark Hollow"
- S3, E10: "The New Neverland"
- S3, E17: "The Jolly Roger"
- S4, E15: "Poor Unfortunate Soul"
- S6, E15: "A Wondrous Place"