Tuwim was born in Łódź, into a family of assimilated Jews. Both of his parents, Isadore and Adele, were educated members of the Litvak intelligentsia and provided Julian with a comfortable middle class upbringing. He was not a particularly diligent student and had to repeat the sixth grade. In 1905 the family had to flee from Łódź to Breslau in order to escape possible repercussions following Isadore's involvement in the Revolution of 1905.

Initially Tuwim's poetry, even more than that of the other "Skamandrites", represented a decisive break with turn-of-the-century mannerism. It was characterized by an expression of vitality, optimism, and praise of urban life. His poems celebrated introduction to the everyday life in a city, with its triviality and vulgarism. In his poems Tuwim often used vernacular language and slang as well as poetic dialogue.

The collections "Czyhanie na Boga" (In Lurking for God (1918)), "Sokrates tańczący" (The Dancing Socrates (1920)), "Siódma jesień" (The Seventh Autumn (1922)), and "Wierszy tom czwarty" (Volume Four of Poems (1923)) are typical of his early work. In his later collections — "Słowa we krwi" (Words in Blood, 1926)), "Rzecz Czarnoleska" (A Tale from Czarnolas) (1929), "Biblia cygańska" (A Gypsy Bible (1933)) and "Treść gorejąca" (A Burning Matter (1933)) Tuwim became restless and bitter, and wrote with fervor and vehemence about the emptiness of urban existence. He also drew more heavily from romantic and classicist traditions, while perfecting his form and style, and becoming a virtuoso of word and language.

From the very beginning and throughout his artistic career, Tuwim was satirically inclined. He supplied sketches and monologues to numerous cabarets. In his poetry and columns, he derided obscurantism and bureaucracy as well as militaristic and nationalistic trends in politics. His best satiric poem is regarded to be the burlesque, "Bal w Operze" (The Ball at the Opera, 1936).

In 1918 Tuwim co-founded the cabaret, "Picador", and worked as a writer or artistic director with many other cabarets such as "Czarny kot" (Black Cat 1917–1919), "Qui pro Quo" (1919–1932), "Banda" The Gang and "Stara Banda" The Old Gang (1932–1935) and finally "Cyrulik Warszawski" (Barber of Warsaw 1935–1939). Since 1924 Tuwim was a staff writer at "Wiadomości Literackie" (Literary News) where he wrote a weekly column "Camera Obscura". He also wrote for the satirical magazine "Szpilki" (Pins).

Tuwim displayed his caustic sense of humor and unyielding individuality in works such as "Poem in which the author politely yet firmly implores the vast hosts of his brethren to kiss his arse." Here, Tuwim systematically enumerates and caricatures various personae inhabiting European social scene of the mid-1930s -- 'perfumed café intellectuals', 'drab socialists', 'fascist jocks', 'Zionist doctors', 'repressed Catholics' and so on, and ends each stanza by asking each to perform the action indicated in the title. The poem ends with a note to the would-be censor who would surely be tempted to expunge all mention of this piece for its breach of 'public standards.' This stanza ends just like the others as the censor fulfills his role.

His poem "Do prostego człowieka" (To the Common Man), first published in October 7, 1929 in "Robotnik" (Workman), started a storm of personal attacks on Tuwim, mostly from antisemitic right wing circles criticizing Tuwim's pacifistic views.

Julian's aunt was married to Adam Czerniaków, and his uncle from his mothers side was Arthur Rubinstein.

In 1939, at the beginning of World War II and Nazi Germany's occupation of Poland, Tuwim emigrated first through Romania to France, and after France's capitulation, to Brazil, by way of Portugal, and finally to the USA, where he settled in 1942. In 1939-41 he collaborated with the émigré weekly "Wiadomosci Polskie", but broke off the collaboration due to differences in views on the attitude towards the Soviet Union. In 1942-46 he worked with the monthly "Nowa Polska" published in London, and with leftist Polish-American newspapers. He was affiliated with the Polish section of the International Workers Organization from 1942. He was also a member of the Association of Writers From Poland (a member of the board in 1943).

During this time he wrote "Kwiaty Polskie" (Polish Flowers), an epic poem in which he remembers with nostalgia his early childhood in Łódź. In April 1944 he published a manifesto, entitled "My, Żydzi Polscy" (We, Polish Jews).