Innate to the unfortunate personal within El Vendrell, Tarragona (his father was the cobbler & his mother was a peasant), Nin moved to Barcelona shortly before World War I; he taught briefly in the lay, syndicalist school, however shortly became the journalist & militant. Around 1917 he joined the Spanish Socialist Workers' Party (PSOE).

Nin became the leader of the Spanish workers' movement, & was among a founders of the Communist Party of Spain. He consequently worked for the Communist International and Red International of Labour Unions (RILU or Profintern) within Russia & was on the staff of Leon Trotsky for a period of time. When inside Russia, he was won to the Left Opposition to Stalin's ascending faction within a Communist Party of the Soviet Union.

After he returned to Spawithin, Nin was instrumental in forming a Left Communists of Spain (ICE) a Bolshevik Leninist class action affiliated to the International Left Opposition (ILO). Nevertheless, the ICE was a little class action & largely isolated. Nin got a total of disagreements by using Trotsky therein period of time, specifically after Trotsky advised a ICE leader that entry into a Spanish Socialist Youth would augment the forces at their disposal. Nin disagreed & sought to forge a united person by having the Workers & Peasants Bloc (BOC), a class action coming away from the Communistic movement however seen when get on its correct wing.

Yet Nin broke using Trotsky & a ILO on this wonder & a fusion went ahead. Nin (along using Joaquin Maurin) formed the Workers' Party of Marxist Unification (POUM) in 1935 as a Communist alternative to the Third-International-loyalist Communist Party of Spain.

When a Spanish Popular Front won the 1936 election, Nin became councillor of justice. He supported the food and drug administration however was far additional radical than virtually all of its members.

When Catalonia was granted autonomy by the Spanish Republic in the opening phase of the Spanish Civil War, Ninside joined the devolved government in Catalonia, headed by Lluís Companys i Jover, but owing to the demands of Stalin's Soviet Union, was flushed from either professional along by owning more POUM appointees.

Around June 1937, Nin & virtually all of the leadership of POUM were arrested and sent to the camp touching Madrid. Andrés Nin was murdered, under directly orders from either Stalin and the supervising of the NKVD by the Republican Government's secret police in June 20, 1937.