The protagonist and narrator of the book, Karana spends eighteen years as the only living person on the island of the blue dolphins. When the book opens, she is twelve years old, the daughter of the chief of Ghalas-at. Resourceful and resilient, she survives on her own after her tribe deserts Ghalas-at. She learns to live in harmony with her island, but longs for the human contact she is missing.
The leader of the pack of wild dogs that lives on Ghalas-at, Rontu was brought to the island by the Aleuts. Unlike the other dogs, which have brown fur and brown eyes, Rontu has yellow eyes and gray fur (he is also much larger than the average dog of the island). Though Rontu and Karana are enemies at the beginning of the novel, they become friends after Karana injures Rontu and then nurses him back to health.
Tutok is an Aleut girl that comes with a hunting party after Karana has spent a few years on the island. Tutock happens upon Karana's dwelling and the two eventually become friends, though Tutok eventually has to leave with her people. Tutok is the first human contact Karana has in many years, and reminds her just how lonely she I upon the island.
Karana's six-year-old brother is a very enthusiastic boy. He is confident and proud of himself and his heritage, and often rash (as young boys are wont to be). It is such rashness that causes him to be left behind when his tribe leaves Ghalas-at, and such confidence that is the cause of his trouble with the wild dogs.
Another Native American tribe that often comes to Ghalas-at to hunt otter. Early in the novel, conflict between the two tribes results in a bloody battle that kills many men of Ghalas-at. Karana considers them her enemies because of what they have done to her people, but eventually she befriends one of them. They come to the island in a boat with red sails.
Karana's fourteen-year-old sister, Ulape likes jewelry and boys. Before she leaves the island, she paints the sign on her face that menas she is unmarried. Later in the novel, Karana often finds herself wondering what happened to her sister.
The chief of the people of Ghalas-at at the beginning of the book. A strong and confident leader, Chowig is mistrustful of the Aleuts that come to Ghalas-at to hunt. He refuses to allow the Aleuts to take advantage of his people, and this, in the end, is his downfall.
The Russian leader of the Aleut expedition to Ghalas-at, Orlov is snide and deceptive. He is profit-oriented and willing to take what he wants.
Chosen as chief after Chowig is killed by the Aleuts, Kimki is an old and venerated member of the tribe. It is he that goes out alone to prepare a new home for the people of Ghalas-at after their battle with the Aleuts.
Matasip takes over as chief in Kimki's absence, and is in charge the day everyone leaves the island. He is an effective leader, though not very important to the plot.
A young man of the tribe that Karana's sister, Ulape, has a crush on. Nanko thought he saw Ramo board the boat the day Ramo and Karana are left behind, but is mistaken.
One of the birds Karana tames. "Tainor" is the name of a boy Karana liked before she was stranded on the island.
Another of the birds Karana tames. "Lurai" is the name Karana wishes she had had instead of Karana.
An otter that Karana finds injured after the Aleuts have left her island. Karana cares for Mon-a-nee until her returns to the sea, and later sees her with her babies playing in the ocean.
Literally "son of Rontu," this is Rontu's son, who Karana befriends after Rontu dies. Rontu-Aru is so similar to Rontu that Karana often forgets that they are not one in the same.
White men from the country to the east. These people come to bring Karana's tribe away from Ghalas-at. Eighteen years later, a different group of white men take Karana, too. The White men's boat has white sails.