Dory, the charming regal blue tang, finds herself lost and alone after being separated from her parents, Jenny and Charlie, during her childhood. Growing up with the struggle of short-term memory loss, she gradually forgets them until fate brings her together with Marlin, a clownfish on a quest to find his missing son, Nemo.
Fast forward one year, and Dory now happily resides in the reef alongside Marlin and Nemo, who have become her close friends and neighbors. One day, she experiences a flicker of memory about her parents and recalls that they live at the "Jewel of Morro Bay, California." Determined to reunite with them, Dory embarks on a grand adventure, with Marlin and Nemo standing by her side.
Enlisting the help of Crush, their spirited sea turtle friend, the trio rides the California Current toward California. However, their journey takes a perilous turn when Dory inadvertently awakens a giant squid, endangering Nemo. In her effort to protect her friends, Dory finds herself captured by staff from the Marine Life Institute.
Once there, Dory is placed in quarantine and tagged for transfer to an aquarium in Cleveland, Ohio. While inside, she encounters Hank, a gruff yet kind-hearted seven-legged octopus who fears being released back into the cold ocean. Hank strikes a deal with Dory: he will assist her in locating her parents if she helps him escape his fate of being returned to the sea. During her time at the institute, Dory meets Bailey, a beluga whale, and her childhood companion Destiny, a nearsighted whale shark. With their help, she uncovers the lost memories of how she became separated from her parents, realizing she was swept away by an undertow current into the pipes as a child.
Meanwhile, Marlin and Nemo refuse to give up on Dory. They team up with a couple of California sea lions and an adventurous common loon named Becky to infiltrate the Marine Life Institute and locate their friend. When they learn from a group of blue tangs that Dory's parents had ventured out long ago to search for her and were presumed lost, it weighs heavily on Dory, filling her with despair.
In a twist of fate, Hank accidentally drops Dory into a drain, sending her back into the ocean. There, she discovers a trail of shells, a nostalgic reminder of the paths her parents had laid down for her to ultimately find her way home. Following the trail leads her to a tire, where she experiences an emotional reunion with Jenny and Charlie. They share heartfelt stories of how they remained near the reef for years, laying shells, hoping she'd return to them.
As the story unfolds, Marlin, Nemo, and Hank find themselves on a truck transporting various sea creatures to Cleveland. Destiny and Bailey come to the rescue, breaking free from their exhibit to help Dory save her friends. With her encouragement, Hank decides to return to the sea with Dory, facilitating a daring escape that results in the crash of the truck into the ocean, liberating all the aquatic captives.
Finally, Dory joyfully returns to the reef with her parents, where they join Marlin and Nemo, now a true family, embracing a new life together filled with love and adventure.
> In a humorous post-credits scene, the Tank Gang, still trapped in their plastic bags after floating across the Pacific Ocean for an entire year, arrive in California, only to be met with a grim fate as they are apprehended by the Marine Life Institute staff.
