In 1923, he opened an architectural practice at 35 rue de Sèvre in Paris with his cousin Charles Édouard Jeanneret, better known as Le Corbusier. They collaborated for some twenty years, and were among the fifteen architects who contributed to the modernist Weissenhof Estate exhibition in 1927.
1940 Pierre Jeanneret leaves German-occupied Paris to join a resistance unit in Grenoble with his colleagues Georges Blanchon and Jean Prouvé, suspending his collaboration with Le Corbusier until 1950.
1950 Le Corbusier and Jeanneret begin a project in Chandigarh, India, designing and producing low-cost buildings for the community. Le Corbusier abandoned the project halfway through, and Pierre Jeanneret became Chief Architect and urban development designer. He stayed in India for 15 years, and Chandigarh became a benchmark of modern architecture.
Pierre Jeanneret's contribution to his association with Le Corbusier was no small one. He often drew the first sketches of plans, then gradually retouched and refined them with Le Corbusier. He knew how to stimulate his cousin's imagination or temper it with his own realism. He also played an important role in ensuring the continuity of the office, coordinating and controlling technical aspects.