The character known as Grand Père, often referred to by the villagers as l'Oncle de l'Alpe, is a central figure in the story of Heidi. He is the paternal grandfather of the young heroine, having lost his son Tobias, a carpenter who was killed by a falling beam at work, and his daughter-in-law Adelaide, who died from grief and fragile health soon after. Before retreating to the mountains, Grand Père led a troubled life. He was known as an inveterate gambler who was forced to sell the family estate to pay his debts. After deserting the army, he settled in the village of Dörfli with his wife and son, but following her death and later the death of his son, he chose to become a hermit. He lives reclusively in a small chalet above Dörfli, cultivating a reputation that fuels the villagers' fear and mistrust. Dark rumors circulate in the valley, including speculation that he killed a man in his youth, which contributes to his fearsome and mysterious reputation.

In terms of personality, Grand Père is initially presented as a severe, gruff, and profoundly misanthropic individual. He trusts no one, does not attend church, and almost never descends into the village, even in winter. When his granddaughter is first left with him by her aunt Dete, he receives her harshly, resenting the intrusion into his carefully guarded solitude. He is a man of few words, hardened by a lifetime of loss and rejection by the community. However, beneath this rugged exterior lies a deep capacity for devotion and attachment, which is almost exclusively reserved for Heidi. His granddaughter’s boundless enthusiasm, curiosity, and joyful nature quickly dismantle his defenses. He becomes dedicated to her happiness and well-being, showing a tenderness that he conceals from the rest of the world. His motivation shifts from a desire to live in total peace and isolation to a quiet, fierce determination to protect Heidi and ensure she has a good life, even if it means confronting his own past and the society he has rejected.

Grand Père’s primary role in the story is that of a guardian and a reluctant father figure who provides Heidi with a home and a sense of belonging she had never known. His existence is the anchor for her life in the Alps. The relationship between Heidi and her grandfather is the emotional core of the narrative. Through her, he reconnects with the world he abandoned. For instance, at Heidi's simple request, he agrees to repair the dilapidated house of Pierre's grandmother, a blind, elderly woman living in the valley. This act of kindness is significant because he does it not for the gratitude of the villagers, whom he scorns, but purely out of love for Heidi. Similarly, he defies his nature by saving a group of hunters lost in a violent snowstorm. The most profound development for his character occurs after Heidi is taken to Frankfurt. Her departure leaves him devastated and reclusive once more, but her eventual return solidifies a transformation. He begins to reconsider his isolated existence, and gradually, he resolves to reconnect with the community. The final stage of his development is his decision to leave his mountain retreat and spend the winter in Dörfli itself so that Heidi can attend school. This action symbolizes his full redemption and reconciliation with humanity, as he regains the respect of the villagers who once shunned him.

Regarding notable abilities, Grand Père is highly skilled in traditional alpine crafts and survival. He is a proficient carpenter and woodworker, as evidenced by the objects he creates in his workshop to trade for supplies. He also makes cheese and possesses an intimate knowledge of the mountain terrain, its secrets, and its dangers. He is a capable teacher, patiently instructing Heidi on how to make cheese, find wild strawberries and chestnuts, and navigate the natural world around her. His skills are entirely practical, born from a life of self-sufficient isolation in a harsh environment, and he applies them with quiet competence and a deep respect for nature.