In 1956, he left Hungary with his family. Between 1956 and 1958, he lived in Germany, and in 1958, he moved to France, where he lived until his death. Despite having graduated from the École Supérieure des Beaux-Arts in Paris and being a student at the École des Arts Décoratifs, he considered himself a self-taught artist. Starting in the early 1970s, he used himself as a model for fifteen years. Initially, he painted simple portraits, but over time, these were replaced by more complex, often aggressive and theatrical setups involving various objects. Many saw narcissism and masochism in his paintings, though the reason for his constant self-depiction was that he was disturbed by others during his work, even the presence of a model. He did not copy ready-made photographs but rather created them as part of his artistic process, which involved composing the scene, lighting the model, positioning their body, and choosing their environment and clothing colors.

From 1988 onward, he painted mostly male figures, with his sons often serving as models. In line with his usual style, these figures were wrapped in cloths, accompanied by unusual objects. However, in his still lifes, he focused mainly on bottles, fruits—apples, oranges, peaches, pears. The backgrounds of his paintings were generally neutral, simple walls, yet he meticulously painted even their cracks.

His first exhibition with Hungarian ties was held in 2001 at the Hungarian Institute in Paris, organized by Kálmán Makláry, who also organized his later exhibitions in Hungary. His first exhibition in Hungary, exactly 50 years after he left the country, took place in 2006, with 15 of his works displayed at the Erdész & Makláry Fine Art gallery in Budapest. From April 13 to June 3, 2007, he had a retrospective exhibition in Debrecen at the MODEM, where visitors could see 70 of his paintings.

He studied at two renowned institutions, but he always considered himself a self-taught artist. Critics often categorized István Sándorfi among hyperrealist artists, but he never identified himself as one. His meticulous paintings always contained intentional flaws (a blurred hand, a smudged foot), breaking the photorealistic effect of the paintings.