As the story opens, Buck, a powerful St. Bernard-Scotch Collie, lives a comfortable life in Californias Santa Clara Valley as the pet of Judge Miller. Manuel, the gardeners assistant, steals Buck and sells him to pay a gambling debt. Shipped to Seattle, Buck is harassed in his crate and given nothing to eat or drink. Released from the crate, he confronts and is beaten by the man in the red sweater, and is taught to respect the club. Buck is bought by a pair of French-Canadian dispatchers from the Canadian government named François and Perrault, who take him to the Klondike region of Canada and train him as a sled dog where he quickly learns how to survive the cold winter nights and the pack society by observing his teammates. He and the vicious, quarrelsome lead dog, Spitz, develop a rivalry. Buck eventually beats Spitz in a fight to the death. Spitz is killed by the pack after his defeat and Buck becomes the leader of the team.
The sled dog team is sold to a Scottish half breed man working in the mail service. The dogs carry a heavy load and the journey they make is tiresome and long. After a long time with this owner, the dogs are beat down and so tired that they can no longer make the trek. Some of the dogs are shot and some are eaten by wolves.
Buck is then sold to a trio of stampeders; Hal, Charles, and a woman named Mercedes. They have little experience of survival in the Northern wilderness, struggle to control the sled, and ignore warnings about the dangers of travel during the spring melt. They over feed the dogs and starve them when the food supply runs out. On their journey they meet John Thornton, an experienced outdoorsman, who notices that the dogs have been poorly treated and are in a weakened condition. He warns the trio against crossing the river, but they refuse his advice and order Buck to move on. Exhausted, starving, and sensing the danger ahead, Buck refuses and continues to lie unmoving in the snow. After Buck is beaten by Hal, Thornton recognizes him to be a remarkable dog. Disgusted by the drivers treatment of Buck, Thornton cuts him free from his traces and tells the trio hes keeping him, much to Hals displeasure. After some argument, the trio leaves and tries to cross the river, but as Thornton warned, the ice gives way and the three fall into the river along with the neglected dogs and sled.
Thornton nurses Buck back to health, and Buck comes to love him and grows devoted to him. Buck saves Thornton when the man falls into a river. Thornton then takes him on trips to pan for gold. During one such trip, a man wagers Thornton on Bucks strength and devotion; the dog wins the bet by breaking a half-ton sled free of the frozen ground, pulling it 100 yards, and winning $1600 in gold dust for Thornton. While Thornton and his friends continue their search for gold, Buck explores the wilderness and begins to socialize with a timber wolf from a local pack. One night, he returns from a short hunt to find that his beloved master and the others in the camp have been killed by a group of Yeehat Indians. Buck eventually kills the Indians to avenge Thornton, and he then follows the wolf into the forest and answers the call of the wild. At the end of the story, Buck returns each year, as the Ghost Dog of the Northland Legend, to mourn at the site of Thorntons death.