In 1939, Austrian mountaineer Heinrich Harrer (Brad Pitt) leaves behind his pregnant wife to join Peter Aufschnaiter (David Thewlis) in a team attempting to summit Nanga Parbat in the British Raj (present-day part of Pakistan). When World War II begins in 1939, they are arrested by the authorities for being enemy aliens and imprisoned in a prisoner-of-war camp in Dehradun in the Himalayan foothills, in the present-day Indian state of Uttarakhand. Harrer's wife, Ingrid (Ingeborga Dapkūnaitė), who has given birth to a son he has not seen, sends him divorce papers from Austria.
In 1944, Harrer and Aufschnaiter escape the prison and cross into Tibet. After being initially rejected by the isolated nation, they manage to travel in disguise to the Tibetan capital city of Lhasa. There, they become the house guests of Tibetan diplomat Kungo Tsarong (Mako). The Tibetan senior official Ngawang Jigme (BD Wong) also extends friendship to the two foreigners with gifts of custom-made Western suits. Aufschnaiter falls in love with the tailor, Pema Lhaki (Lhakpa Tsamchoe), and marries her. Harrer opts to remain single, both to focus on his new job of surveying the land and not wishing to experience another failed relationship.
In 1945, Harrer plans to return to Austria upon hearing of the war's end. However, he receives a cold letter from his son, Rolf, rejecting Harrer as his father, and this deters him from leaving Tibet. Soon afterwards, Harrer is invited to the Potala Palace and becomes the 14th Dalai Lama's (Jamyang Jamtsho Wangchuk) tutor in world geography, science, and Western culture. Harrer and Dalai Lama end up befriending each other.
Meanwhile, political relations with China sour as they make plans to invade Tibet. Ngawang Jigme leads the Tibetan army at the border town of Chamdo to halt the advancing People's Liberation Army. However, he ends up surrendering and blows up the Tibetan ammunition dump after the one-sided Battle of Chamdo.
During the treaty signing, Kungo Tsarong tells Harrer that if Jigme had not destroyed the weapons supply, the Tibetan guerrillas could have held the mountain passes for years; long enough to appeal to other nations for help. As the Chinese occupy Tibet, Harrer condemns Ngawang Jigme for betraying his country, declaring their friendship over. Out of anger, Harrer further humiliates the senior official by returning the jacket that Ngawang Jigme gave him as a present, a grave insult in Tibetan culture, as well as by throwing him onto the ground.
Harrer tries to convince the Dalai Lama to flee, but he refuses; not wanting to abandon his people. The Dalai Lama encourages Harrer to return to Austria and be a father to his son. After the enthronement ceremony, in which the Dalai Lama is formally enthroned as the spiritual and temporal leader of Tibet, Harrer returns to Austria in 1951.
Harrer's son, Rolf, refuses to meet him at first, but Harrer leaves a music box that the Dalai Lama gave him and this piques the boy's interest. Years later, Harrer and Rolf (now a teenager) are seen mountain-climbing together, suggesting that they have mended their relationship.
Brad Pitt as Heinrich Harrer
David Thewlis as Peter Aufschnaiter
BD Wong as Ngapoi Ngawang Jigme
Mako as Kungo Tsarong
Danny Denzongpa as Regent
Victor Wong as Chinese 'Amban'
Ingeborga Dapkūnaitė as Ingrid Harrer
Jamyang Jamtsho Wangchuk as Dalai Lama Tenzin Gyatso, 14 years old
Sonam Wangchuk as Dalai Lama Tenzin Gyatso, 8 years old
Dorjee Tsering as Dalai Lama, 4 years old
Lhakpa Tsamchoe as Pema Lhaki
Jetsun Pema as The Great Mother
Ama Ashe Dongtse as Tashi
Ric Young as General Chang Jing Wu
Ven. Ngawang Chojor as Lord Chamberlain
based on the 1952 book of the same name by Austrian mountaineer Heinrich Harrer