Like many other fairies from Pixie Hollow, Tinker Bell (Mae Whitman) attends fairy camp on the mainland. When she attempts to go find some lost things, Vidia (Pamela Adlon) asks her if she's going to the human house, which isn't too far from camp. The question makes Tinker Bell curious and she eventually sneaks off. Vidia follows behind to watch over her. When Tink reaches the human house, she is amazed by their "horseless carriage". She takes the time to flitter around under the car, while Vidia tries to get her to leave. Eventually they do, but on their way back to camp, Tink and Vidia stumble upon a fairy sized house made by Elizabeth Griffiths (Lauren Mote), a human girl who wishes to meet a real fairy. Tinker Bell immediately heads in to investigate, despite Vidia's constant warnings to leave. Tink claims it to be perfectly safe, so Vidia uses her wind to slam the door in an attempt to give Tink a little scare but it unintentionally locks Tink inside.
When Lizzie begins to approach the house, Vidia tries to free Tink but it's no use. Lizzie discovers Tink inside the house and takes her to her home. She prepares to show her father, Dr. Griffiths (Michael Sheen), but upon witnessing all the butterflies he has pinned in display cases for research, she decides to keep Tink a secret. Meanwhile, Vidia rallies Rosetta (Kristin Chenoweth), Iridessa (Raven-Symoné), Fawn (Angela Bartys), Silvermist (Lucy Liu), Clank (Jeff Bennett), and Bobble (Rob Paulsen) to rescue Tink.
Back at the human house, Lizzie's reveals her fascination of fairies to Tink. Tink is flattered by the child's obsession, and since it's raining outside, Tink decides to teach her nearly everything about fairies. She tells her how light fairies make rainbows, how animal fairies paint butterflies, and much more. They record their information in a new research book given to Lizzie by her father. During this time, Tink and Lizzie have grown a great friendship, but after a while, the rain dies down, and Tink is able to return to camp. She Gives a sad Lizzy a hug and makes her way out but before she leaves, she watches Lizzie attempt to show her father the research.
Unfortunately, Dr. Griffiths is too busy fixing the house's leaks, as usual, to pay Lizzie any mind. Tink returns and decides to fix the leaks so Lizzie may spend more time with her father. After she does, she makes the choice to release a captive butterfly Dr. Griffiths was planning on showing to a group of scientists, which causes a stern and suspicious Dr. Griffiths to ground Lizzie. To make up, Tink shows Lizzie how to fly, and when her father finds footprints on the ceiling, she tells him about Tink. He furiously discards the claims and begins to throw all her fairy drawings, and research book, into the trash.
Upon seeing this, Tink loses her temper completely and the fairy reveals herself, telling the father off while doing so (though he only hears jingles when she talks). The astonishing sight of a fairy prompts Dr. Griffiths to capture Tink, but Vidia arrives and pushes her out the way. Vidia is then taken by Dr. Griffiths to London for research, but Lizzie and the fairies are able to convince him to think otherwise, which he does. Vidia is freed, and she and Tink form a friendship. Lizzie and her father are now closer than ever.
The voice actors are largely the same as in the previous films.
- Mae Whitman - Tinker Bell, a tinker fairy
- Lauren Mote - Lizzy Griffiths, a nine-year old girl
- Michael Sheen - Dr. Griffiths, a scientist and Lizzy's father
- Pamela Adlon - Vidia, a fast-flying fairy
- Lucy Liu - Silvermist, a water fairy
- Raven-Symoné - Iridessa, a light fairy
- Kristin Chenoweth - Rosetta, a garden fairy
- Angela Bartys - Fawn, an animal fairy
- Rob Paulsen - Bobble, a wispy tinker fairy with large glasses
- Jeff Bennett - Clank, a large tinker fairy with a booming voice / Driver
- Jesse McCartney - Terence, the pixie-dust keeper
- Cara Dillon - Narrator
- Faith Prince - Mrs. Perkins, a neighbor of Lizzy and Dr. Griffiths
- Bob Bergen - Additional Voices