The novel does not have a plot but is rather a series of adventures had by Pippi and her friends. Pippi Longstocking is an orphan who moves into a beautiful home called Villa Villekula when she leaves her father's ship after he is tragically blown overboard. She takes with her a big suitcase filled with hold coins and her pet monkey, Mr Nielsson, who was a gift from her father. Next door there is a family with two children, Annika and Tommy, and the three quickly become friends. The day after they meet Pippi they visit her to find her rolling out ginger snap dough on the floor. Pippi invites them to go thing-searching with her and on this jaunt she is excited to find a rusty can. As they head home a boy comes rushing out of a nearby house, crying, because he is being bullied. Pippi uses her excessive strength to fling the bullies over a nearby tree before she continues on home.
Predictably, the adults in town are not happy that Pippi lives alone and decide she must go to live in a children's home. She eludes the policemen who arrive at the house to escort her there and they feel so foolish that they assure the townspeople that she is really not suited to a children's home, and they she is perfectly gone at the Villa. Because they believe school would be far more fun if Pippi was there, Annika and Tommy convince her to begin attending but it soon becomes evident that she is not suited to school either and attendance soon stops.
When the children learn that the circus has come to town they are very excited and manage to get front row seats. Pippi cannot contain herself and ends up joining in the performance, first riding a horse and standing upright on his back, then wowing the audience with her tightrope-walking skills. Finally she fights with the strong man, Strong Adolf, overpowering him and winning the fight. Of course, her game is growing in town but outsiders have yet to hear about the mysterious strong child who lives alone. When two burglars come to town they call at the Villa Villekula to ask for a sandwich. Pippi obliges and continues to count her hold coins whilst they are eating. The men decide to return later when everyone is in bed, but when they do Pippi keeps them up all night dancing the polka with her, and as they leave, exhausted, and without having managed to actually burgle anything, she gives them a gold coin each as a thank-you.
Tommy and Annika's mother gives them permission to invite Pippi over to play whilst she hosts a coffee morning. Their mother envisages the children playing outside, or in their rooms, but Pippi is hungry and eats all of the cake. She then experiments with making sugar lumps on her tongue much to the annoyance of the adults present. She joins on their conversation but they ignore her until she realizes she has misbehaved and leaves.
Pippi has become used to playing with Tommy and Annika so when they are occupied on an excursion with their parents she decides to ride into town after doing errands all morning. She sees a four-story building on fire and realizes there are two children trapped on the top floor. Pippi enlists the help of Mr Nielsson to rescue both children to rapturous applause.
The book closes as Pippi celebrates her birthday hosting Tommy and Annika at her birthday party where she announces that she wants to be a pirate when she grows up.