When Boy is taken to be in a circus, Tarzan and Jane go to New York to find him and bring him home.
Tarzan (Johnny Weissmuller), Jane (Maureen O'Sullivan), and Boy (Johnny Sheffield) see an airplane landing. Buck Rand (Charles Bickford) wants to hunt lions and aims at Tarzan, who breaks his rifle and tells them to leave. Boy wants to see the airplane and rides an elephant to it. Boy makes three elephants do tricks. Buck offers Boy a ride, but pilot Jimmie Shields (Paul Kelly) tells Boy to go away. When Manchester Montford (Chill Wills) is caught in a net, Boy distracts a lion to save him until Buck shoots the lion. Natives attack, and Boy calls Tarzan. While swinging on vines, Tarzan and Jane fall. Natives start a fire. Buck takes Boy on the plane, and they take off. Cheetah (chimpanzee) rescues Tarzan and Jane.
Tarzan and Jane travel and learn where Boy was taken. Jane and Tarzan buy clothes, using gold for credit, and fly to New York. They look for Jimmie and take a taxi to the hotel with Cheetah. Tarzan takes a shower in his suit. Cheetah eats and plays with lotions and make-up. Jane and Tarzan go to a club to find Jimmie, and Cheetah follows. Jimmie's friend Connie (Virginia Grey) sings and tells them of Buck's circus. Boy talks to an elephant and Manchester. Col. Sergeant (Cy Kendall) and Buck get a $100,000 offer for Boy from Brazil. Tarzan and Jane ask Sergeant for Boy as Buck leaves with him. Jimmie arrives with police and persuades Jane and Tarzan to go to court. Tarzan testifies how he taught Boy to live in the jungle; but Jane admits she is not Boy's mother. Tarzan gets angry and grabs Buck. Tarzan is detained. Jane asks him to get Boy, and Tarzan escapes out the window and climbs up to the roof and down a drainpipe. He takes a taxi that stops on the Brooklyn Bridge, and from a cable Tarzan dives into the river.
At the circus Manchester tries to stop Buck and Sergeant but is shot. Boy goes up on the trapeze. Tarzan arrives but is caught in a net and put in a cage. Tarzan gets elephants to help him. Buck and Sergeant take Boy in a car, but elephants trap them. Tarzan rescues Boy, and the car crashes. Judge Abbotson (Russell Hicks) suspends Tarzan's sentence and plans to fish in Africa. In Africa in the final scene Tarzan, Jane, and Boy dive and swim.
The natural life of the jungle is contrasted to the
artificial city as the strong virtues of Tarzan prevail over greed.