Dory, a regal blue tang, gets separated from her parents as a child. As she grows up, Dory attempts to search for them, but gradually forgets them due to her short-term memory loss disability. In the flashback of the previous film, Finding Nemo, after accidentally running into Marlin, a clownfish who is looking for his missing son, Nemo, she joins him on his journey.
One year later, Dory has joined Marlin and Nemo on their reef. One day, Dory has a flashback and remembers that she has parents. She decides to look for them, but finds her memory problem an obstacle. She remembers that they lived at the Jewel of Morro Bay across the ocean in California.
Marlin and Nemo accompany Dory. With the help of Crush, a sea turtle friend, they ride a water current to California. Upon arrival, Dory accidentally awakens a squid, who immediately pursues them, almost devouring Nemo. Marlin berates Dory for endangering them. Her feelings hurt, Dory travels to the surface to seek help and is captured by staff members from the nearby Marine Life Institute after getting entangled in six pack rings.
Dory is placed in the quarantine section and tagged. There she meets a grouchy but well-meaning octopus named Hank. Dory’s tag shows that she will be sent to an aquarium in Cleveland. Due to a traumatic ocean life, Hank wants to live in the aquarium instead of being released back into the ocean, so he agrees to help Dory find her parents in exchange for her tag. In one exhibit, Dory encounters her childhood friend Destiny, a nearsighted whale shark who used to communicate with Dory through pipes, and Bailey, a beluga whale who mistakenly believes he has lost his ability to echolocate. Dory subsequently has flashbacks of life with her parents and struggles to recall details. She finally remembers how she was separated from her parents: she overheard her mother crying one night, left to retrieve a shell to cheer her up, and was pulled away by an undertow current.