Spanish painter, he stood out as a muralist.

He was born on December 21, 1874, in Barcelona (Spain). He was the son of Domingo Sert Rius, an industrialist and politician, and María Badía Capdevila. He was the brother of Francisco, an industrial engineer and conde de Sert; Domingo, a politician and industrialist; and Dolores, Carmen, and Mercedes Sert Badía. He was the uncle of lawyer Antonio Sert; architect José Luis Sert; and Francisco Sert, heir to the noble title of his father Francisco. He was married to Russian pianist María Sofía Olga Zenajda Godebska, known as Misia Sert, and to Georgian sculptor Roussadana Mdiwani in his second marriage.

He left the family textile business and took drawing classes at the Escuela de Artes y Oficios de Barcelona. He joined the Círculo Artístico de Saint-Luc led by José Torrás y Bages, bishop of Vic, who would later commission him to decorate the cathedral of this town in Barcelona. In 1900, he participated in the Exposition Universelle in Paris, where he set up his studio and became the great European muralist of the 20th century. His studio was frequented by figures such as Maurice Denis, Edgar Degas, Paul Valéry, André Gide, and Paul Claudel. In Paris, he exhibited at the Salon d'Automne in 1907 and at the Musée du Jeu de Paume in 1926. He stood out as a theatrical decorator, creating stage designs for the Ballets Russes of Diaghilev, such as "La légende de Joseph"(1914), "Las Meninas" (1916), and "Le astuzie femminili" (1920); and for the opera "Goyescas" by Enrique Granados, performed at the Teatro alla Scala in Milan (1938). In this role, he designed the set and stage design for the scenic cantata "Atlántida" (1927-1946) by Manuel de Falla, a project that was never completed due to the death of both artists.

During World War I, he acted as a liaison between the French government and Catalan manufacturers who supplied equipment to the allied army, for which he was awarded the Ordre National de la Légion d'Honneur of France. He was appointed cultural attaché at the Spanish Embassy in Paris by the government of the Spanish Second Republic. During the Spanish Civil War, he participated in various operations aimed at safeguarding the works of the Museo del Prado, which were placed under the protection of the Sociedad de Naciones based in Geneva. The destruction of his work in Vic brought him closer to the rebel side, which led to his appointment, along with Eugenio d'Ors, to inventory the paintings and artworks located in Geneva in 1939. In 1940, he began working on a new project for the Vic Cathedral, which was inaugurated just days before his death in 1945.

He was awarded the Gran Cruz de Alfonso XII and named a member of the Real Academia de Bellas Artes de Madrid. Some of his works include "Los recuerdos maravillosos" (1916), "La fortuna" (1917-1920), "Pinturas de las cuatro estaciones" (1917-1920), "Murales de las bodas de Camacho"(1930-1931), "Los equilibristas" (1932), "Intercesión de Santa Teresa de Jesús en la Guerra Civil española" (1937), "Murales de los triunfos de la humanidad" (1932-1941), and "Las evocaciones españolas" (1942). He passed away on November 27, 1945, in Barcelona (Spain).