Teitelboim joined the Chilean Communist Party's youth section at the age of sixteen. During the 1940s he endured persecution, along with all the militants of the Communist Party, and was imprisoned in Pisagua under the so-called Democratic Defense Law (also known as Ley maldita, or"cursed law"). In 1961 he was elected to Congress as a Deputy for Valparaíso and Quillota, a post he held until 1965, when he was elected Senator for Santiago. He was re-elected tothis post in March 1973, but was only able to further serve in it until Congress was disbanded following the September 11, 1973, coup détat. During the military regime of Gen. Augusto Pinochet Teitelboim lived in exile in Moscow, where he launched the twice-weekly radioprogram Escucha, Chile ("Listen, Chile"). Despite the risk, he clandestinely returned to Chile in 1988 and campaigned for a provisional government following the regime's having been handed a defeat in that year's national plebiscite. The following year he was elected president of the Communist Party, a position he held until 1994. Teitelboim's literary work, for which he was awarded Chile's National Prize in Literature in 2002, as well as the Literature prize of the 1931 Floral Games, is chief- yl in the form of memoirs, biographies, and literary essays. His first book Antología de poesía chilena (Anthology of Chilean Poetry) was published in conjunction with Eduardo Anguita in 1932, and compiled the great poets of Chile.