Mir studied at the Escola de Belles Arts 'Llotja', and was a member of a group of young artists who painted the fields in the countryside outside Barcelona. "The Cathedral of the Poor", a realistic group portrait of beggars near the famous Temple of the 'Sagrada Familia' during its construction, is among his most important works of this period.
In 1899 Mir settled in Mallorca, at first with painter Santiago Rusiñol and after alone, where he produced extraordinary works. His one-man exhibition in 1901 at the Sala Parés in Barcelona met with public incomprehension, but he was praised by critics as the new great painter of the Catalan landscape. In 1904, an accident and psychiatric illness ended his Mallorcan period. During his convalescence, interned in the psychiatric institute of Reus, Mir produced his most creative work, representing the light and color of the landscape in an, almost, abstract way.
In 1907, Mir won a first-class medal at the fifth Exposició Internacional in Barcelona, and in 1930, he won he medal of honor of the Exposición Nacional de Bellas Artes of Madrid. Joaquim Mir died in Barcelona in 1940.