The novel is narrated by Tommy Stubbins, who meets the doctor while seeking assistance for an injured squirrel and becomes his assistant. In the course of the story, Doctor Dolittle studies the language of shellfish, defends a man falsely accused of murder by translating the testimony of the man's dog, champions the rights of Spanish bulls, and goes on an expedition to the mysterious Spider Monkey Island.
This novel contains examples of:
- Animal Talk: Averted, in that each type of animal has its own separate language. Much of the book deals with Dolittle attempting to learn the language of shellfish and several other aquatic species and requires a scene in which a giant sea snail has to talk to the doctor through a sea urchin, who translates for a starfish, who translates for some dolphins, who translate for Doctor Dolittle.
- Awesome Moment of Crowning: This happens when he is crowned King of Spider-Monkey Island, despite not wanting to be a King. The shouts from the people are so loud they topple a stone which causes the moving Island they are on to stop moving.
- Beastly Bloodsports: While in the Capa Blanca Islands, Doctor Dolittle makes a wager with a powerful nobleman that the noble will end bullfighting in the islands if the Doctor can perform more tricks with a bull than any of the local matadors. He then talks to the bulls and convinces them to help him put on a show so that they won't have to die in the bullring any more.
- Bowdlerize: Current editions, with the blessing of Hugh Lofting's son Christopher, excise some language that is considered racist by today's standards, particularly in the descriptions of African and Native characters.
- Does Not Like Shoes: The doctor is visited by Prince Bumpo, an African prince he befriended in the previous book, who is in England to study at Oxford. Bumpo says that he enjoys England immensely, except for the algebra he must learn and the shoes he must wear, which hurt his head and feet respectively. He cheerfully says that now that he's on break from his studies, he's forgotten the algebra and thrown the shoes over a wall, so all is well.
- First-Person Peripheral Narrator: Tommy Stubbins.
- Good Lawyers, Good Clients: At a trial where the Doctor's old friend is falsely accused of murder, the defense lawyer is a genial, jovial, nice guy, while the prosecutor is described as a "frowning, spluttering, long-nosed" quarrelsome individual.
- Majored in Western Hypocrisy: The African Prince Bumpo comes to England to study at Oxford.
- Make the Dog Testify: A dog called as a witness saves an innocent man from a murder charge, thanks to the doctor's ability to understand Animal Talk, which allows him to serve as an interpreter. First though the doctor proves he can speak to animals by interrogating the judge's dog about what was the judge doing last evening (a testimony the judge hastily interrupts, embarrassed).
- Mighty Whitey: While visiting Spider Monkey Island, Doctor Doolittle turns into a badass fighter against a hostile tribe, brokers peace between the warring tribes, and ultimately gets crowned king of the entire island.
- Traveling Landmass: Spider Monkey Island. Explained as a freak volcanic bubble during island formation creating a huge air pocket to serve as a float. When the rock at the top of the volcano drops down it punches a hole in the bottom to fix the island in place.