Marcel Chaumet (1886–1964) was the son of Joseph Chaumet, who had married into the Morel family and in 1885 took over the house founded by Marie-Étienne Nitot in 1780, giving it his name. He grew up in a house at its height: in 1907 his father moved the workshops and boutique to 12 place Vendôme, where they remain, and in 1925 Chaumet took part in the Paris Exposition internationale des arts décoratifs.
He succeeded his father in 1928, at the height of Art Deco. According to French Wikipedia the house's style under him was marked by geometric forms, contrasts of black and white, semi-precious stones and exotic inspiration, with long sautoirs and bandeaux worn across the forehead for the clients of the Années folles; Italian and English Wikipedia describe jewels growing more geometric in the "boyish" style of the 1920s and more feminine in the 1930s. The house's renown spread into the arts and show business. In 1934 Chaumet sponsored the young jeweller Pierre Sterlé, who was already designing for it, to set up on his own; that same year the house closed, reopening after the Second World War.
He was head of the house when it reopened after the war. In 1958 his sons Jacques and Pierre were appointed joint managing directors. Under them Chaumet opened a watch department, took over Breguet in 1970 and employed Sterlé and René Morin as designers, before the brothers' bankruptcy in 1987 ended family ownership.
Sources on his personal life are thin. The 1934 closure is reported by English and Italian Wikipedia but not explained there.