Dulfi was a watch brand created by Henri Müller & Fils SA of La Chaux-de-Fonds. Although it boasted “since 1925” in advertisements, the brand was established only in the 1950s. It was a successor to the short-lived Mulfi, also from Müller, and lasted through 1977.

Henri Müller & Fils was established by 1927 in the Montbrillant Watch Manufactory at Montbrillant 3 in La Chaux-de-Fonds. The company shared this address with Breitling until 1930, though it is unlikely that there was any business relationship between the two.

Müller's name is always written with an umlaut in legal documents, but the company often omitted this in advertising. It is never written as Mueller, however.

Henri Müller & Fils relocated to Rue du Nord 113 by 1930, a year before a divorce caused Henri Müller to divide ownership of the company's assets between himself and his wife. The company was located at Rue de la Paix 119 starting in 1934 before moving again to Rue du Parc 110 in 1943. All of these were in the hills above La Chaux-de-Fonds, where many new and progressive companies were located. Henri Müller was involved in some way with Delba and is mentioned as a creditor in their 1938 bankruptcy proceedings. But the company's fortunes must have improved, as they began advertising their products and seeking distributors that same year.

In 1942, Henri Müller & Fils launched the Mulfi brand. Initially, Mulfi continued with the same products as Henri Müller & Fils before, and indeed used the same artwork in their advertisements. But Mulfi developed new products after the war and launched a line of watches with automatic movements, slim cases, and even chronographs in 1946.

Also in 1946, Henri Müller & Fils was transformed into a corporation, with Henri Müller's son Georges-Henri becoming President. Georges-Henri soon relocated the company to a workshop in the center of town at Rue Jacob-Brandt 61 and began advertising heavily. The brand used an image of a windmill with a concentric clock. The slogan was “like the wind at the mill for elegant customers you will find quality and beauty.”

The Mulfi brand was dropped by Henri Müller & Fils in 1953, however, replaced by Dulfi.

Dulfi was a member of the association of Chronograph Producers by 1963 and benefitted from the recommendations of industry consultant Georges Caspari to the group Focus on youthful chronograph watches to build international sales volume. The company began producing pillow case watches with striking modern design in the late 1960s, competing with fellow members Enicar and Freco.

By 1970, Dulfi was part of Charles Gigandet SA of Tramelan. The company joined Weiss/White Star, Nestor, and Benguerel.

The Dulfi brand was retired in 1977 and Müller is no longer seen after 1981.