The child of a well-off family, before starting a degree in architecture at the Barcelona School of Architecture he studied painting with the painter Simó Gòmez and at La Llotja, the Barcelona School of Fine Arts, although none of his pictures have been conserved. He later qualified as an architect and it is as such that he is known.

After an early period characterised by eclecticism, he did his work in the Modernista style between 1900 and 1910, after which he went over to a more classical style.

His first jobs as an architect were as assistant to another architect, F. Villar i Carmona, on religious works: restoration of the chapel of Sant Josep in Montserrat Abbey and the making of the altar in the church of Monistrol, which no longer exists. In the course of his career he designed many religious buildings, in large part altruistically, working with Dorotea de Chopitea. The most outstanding of these is the Temple of the Sacred Heart of Jesus (1902; Carretera de Vallvidrera al Tibidabo, 111-117), which was completed by his son, Josep Maria Sagnier Vidal, who was also an architect.

His main customers, however, were members of the bourgeoisie, for whom he built many dwellings, especially in the Eixample district of Barcelona, such as the house for Enric Victorià de la Riva (1897; Ali Bei, 1), adapting the novel features of Modernisme to the new buildings, such as the communicating staircases in the central courtyards.

He worked with J. Domènech i Estapà on the Palau de Justícia in Barcelona (Courthouse, 1887-1908; Passeig de Lluís Companys, 14) and with the engineer Pere Garcia i Fària on the Duana Nova (New Customs House, 1896-1902; Passeig de Josep Carner, 27 - 29). Work of his, such as Casa Dr. Genové (1911; Rambla, 77), can also be found in the Ciutat Vella district of Barcelona.

During the last stage of his career he was the architect of the Diocese of Barcelona, a post which enabled him to obtain the pontifical title of marquis of Sagnier and later, in 1928, to become part of the Pope's family with the post of "secret chamberlain of the cloak and sword".

He was a member of the Sant Jordi Academy of Fine Arts and was the only architect to win the prize awarded annually by Barcelona City Council for the best building three times. He was occasionally involved in politics and became a provincial deputy.

Work by him can also be found in Cuba, Mexico and Australia.