Karana is a practical, twelve-year-old girl belonging to the Nicoleño tribe on the Island of the Blue Dolphins. As the daughter of the chief, she possesses a strong sense of responsibility and often suppresses her emotions to focus on survival and duty. She is highly observant of the natural world and feels a deep, protective instinct toward her family members.

Chief Chowig is the strong and cautious leader of the village of Ghalas-at. He harbors a deep distrust of outsiders due to past exploitation by northern hunters who took advantage of his people. He strictly enforces his village's traditions and laws, prioritizing the fair treatment and safety of the Nicoleño people during tense negotiations over resources.

Ramo is Karana's six-year-old brother, characterized by his excitable and imaginative nature. He views the world with youthful wonder, comparing foreign ships to red whales, but his inquisitive behavior often causes him to wander off or ignore his duties. He heavily relies on his older sister for guidance and protection in their daily lives.

Rontu is a large, fierce dog with wolf-like features who originally belonged to the Aleut hunters. Left behind on the island, he adapts by taking control of the local wild dog pack. His presence poses a significant physical threat, forcing the human inhabitants of the island to remain constantly vigilant.

Captain Orlov is a tall, yellow-bearded Russian man who leads the party of Aleut sea otter hunters. He projects a predatory demeanor, smiling to reveal long teeth while negotiating with the local inhabitants. His primary motivation is profit, and he shows little respect for the islanders or their resources.

Tutok is an Aleut girl accompanying the Russian and Alaskan hunting party to the Island of the Blue Dolphins. She possesses a joyful, generous disposition that contrasts with the aggressive nature of the men in her group. Her presence on the island introduces a new dynamic between the native inhabitants and the outsiders.

Kimki is an elderly, respected member of the Nicoleño tribe who steps into a leadership role during a time of crisis. Recognizing the dire situation of his people, he makes pragmatic, non-traditional decisions regarding the village's division of labor to ensure they do not starve.

Ulape is Karana's fourteen-year-old sister. Following their mother's death, she has taken on significant adult responsibilities within the family. She is highly observant, noticing details that other villagers miss, and takes pride in her work and personal appearance.

Matasaip is a man from the village of Ghalas-at who assumes command when the community faces uncertainty. He focuses on organizing the villagers and preparing evacuation plans in case hostile hunters return to the island.

Nanko is a scout for the village of Ghalas-at. He is responsible for keeping watch over the surrounding waters and delivering urgent news to the village leadership regarding incoming vessels.

Captain Mitriff is a historical figure to the people of Ghalas-at, having led a previous Russian-Aleut expedition to the island years ago. His past exploitation of the villagers serves as the primary reason for their current distrust of outsiders.