A blue tang fish named Dory begins to have fragmented memories of her long-forgotten parents and the life she had before she met Marlin, the clownfish. Suffering from short-term memory loss, Dory recalls a childhood in the Jewel of Morro Bay, California, sparking an urge to embark on a quest to find her family. Despite the challenges her memory issues pose, Dory is determined to reunite with her loved ones. Accompanied by Marlin and his son, Nemo, Dory's pursuit of her past leads the trio out into the broader ocean, beyond the confines of their home on the Great Barrier Reef.

During their journey, the friends encounter a host of new and diverse marine creatures, including a cantankerous octopus named Hank, a nearsighted whale shark named Destiny, and a beluga whale with a head injury-named Bailey, who all play roles in Dory's search for her past. The group faces a series of comedic and perilous situations brought about by Dory's optimistic yet forgetful nature. As they delve deeper into the mystery of Dory's origins, the adventure takes them across the ocean to a marine life institute, where Dory learns that her family may be closer than she ever imagined.