Amat-Piniella was born in Manresa in 1913. His father, Joaquim Amat i Palà, was a confectioner and his mother, Concepció Piniella i Blanqué, was a teacher of music and a painter. He was educated at home by his parents before attending secondary school in Manresa and then beginning a law degree. Amat-Piniella began writing articles and essays at a young age and at the age of twenty he published his first novel. With the advent of the Spanish Second Republic, he threw himself into the political and cultural life of his home town. He became a member of Republican Left of Catalonia (Catalan: "Esquerra Republicana de Catalunya") and in December 1932 he was appointed secretary to the mayor of Manresa. Following the Events of the 6 October (Catalan: "Els fets del 6 d’Octubre") he, along with the mayor and councillors, was imprisoned in the Model Prison in Barcelona (Catalan: ""). In February 1936, he was able to return to his post at the Town Hall, following the victory of the left-wing "Frente Popular" (Popular Front) coalition (in Catalonia and Valencia: "Front d'Esquerres") in the Spanish general elections.