He was born in Villeneuve-sur-Fère (Aisne), into a family of farmers and government officials. His father, Louis-Prosper, dealt in mortgages and bank transactions. His mother, the former Louise Cerveaux, came from a Champagne family of Catholic farmers and priests. Having spent his first years in Champagne, he studied at the lycée of Bar-le-Duc and at the Lycée Louis-le-Grand in 1881, when his parents moved to Paris. An unbeliever in his teenage years, he experienced a sudden conversion at the age of eighteen on Christmas Day 1886 while listening to a choir sing Vespers in the cathedral of Notre Dame de Paris: "In an instant, my heart was touched, and I believed." He would remain a strong Catholic for the rest of his life. He studied at the Paris Institute of Political Studies (better known as Sciences Po).

The young Claudel seriously considered entering a Benedictine monastery, but in the end began a career in the French diplomatic corps, in which he would serve from 1893 to 1936. He was first vice-consul in New York (April 1893), and later in Boston (December 1893). He was French consul in China (1895 – 1909), including consul in Shanghai (June 1895), and vice-consul in Fuzhou (October 1900), in Prague (December 1909), Frankfurt am Main (October 1911), Hamburg (October 1913), ministre plénipotentiaire in Rio de Janeiro (1916), Copenhagen (1920), ambassador in Tokyo (1922 – 1928), Washington, D.C. (1928 – 1933) and Brussels (1933 – 1936). While he served in Brazil during the First World War he supervised the continued provision of food supplies from South America to France. (His secretaries during the Brazil mission included Darius Milhaud, later world-famous as a composer, and who wrote incidental music to a number of Claudel's plays.) In 1930, Claudel received an LL.D. from Bates College.

In 1936 he retired to his château in Brangues (Isère).

Claudel married Reine Sainte-Marie Perrin on 15 March 1906.

In his youth Claudel was heavily influenced by the poetry of Arthur Rimbaud and the Symbolists. Like them, he was horrified by modern materialist views of life. Unlike most of them, his response was to embrace Catholicism. All his writings are passionate rejections of the idea of a mechanical or random universe, instead proclaiming the deep spiritual meaning of human life founded on God's all-governing grace and love.

Claudel wrote in a unique verse style. He rejected traditional metrics in favour of long, luxuriant, unrhymed lines of free verse, the so-called verset claudelien, influenced by the Latin psalms of the Vulgate. His language and imagery was often lush, mystical, exhilarating, consciously 'poetical'; the settings of his plays tended to be romantically distant, medieval France or sixteenth-century Spanish South America, yet spiritually all-encompassing, transcending the level of material realism. He used scenes of passionate, obsessive human love to convey with great power God's infinite love for humanity. His plays were often extraordinarily long, sometimes stretching to eleven hours, and pressed the realities of material staging to their limits. Yet they were physically staged, at least in part, to rapturous acclaim, and are not merely closet dramas. The most famous of his plays are Le Partage de Midi ("The Break of Noon", 1906), L'Annonce Faite a Marie ("The Tidings Brought to Mary", 1910) focusing on the themes of sacrifice, oblation and sanctification through the tale of a young medieval French peasant woman who contracts leprosy, and Le Soulier de Satin ("The Satin Slipper", 1931), his deepest exploration of human and divine love and longing set in the Spanish empire of the siglo de oro, which was staged at the Comédie-Française in 1943. In later years he wrote texts to be set to music, most notably "Jeanne d'Arc au Bûcher" ("Joan of Arc at the Stake", 1939), an "opera-oratario" with music by Arthur Honegger.

As well as his verse dramas, Claudel also wrote much lyric poetry, for example the Cinq Grandes Odes (Five Great Odes, 1907).

Claudel was always a controversial figure during his lifetime, and remains so today. His devout Catholicism and his right-wing political views, both unfashionable stances among many of his intellectual peers, made him, and continue to make him, unpopular in many circles.

His address of a poem ("Paroles au Marechal", "Words to the Marshal") to Marshal Philippe Pétain after the defeat of France in 1940, commending Petain for picking up and salvaging France's broken, wounded body, has been unflatteringly remembered, though it is less a paean to Petain than a patriotic lament over the condition of France. As a Catholic, he could not avoid a certain sense of bitter satisfaction at the fall of the anti-clerical French Third Republic. However, accusations that he was a collaborationist based on the 1940 poem ignore the fact that support for Marshal Petain and the surrender was, in the catastrophic atmosphere of defeat, emotional collapse and exhaustion in 1940, widespread throughout the French populace (witness the large majority vote in favour of Petain and the dissolution of the Third Republic in the French Parliament in 1940, with support stretching across the political spectrum). Claudel's diaries make clear his consistent contempt for Nazism (condemning it as early as 1930 as "demonic" and "wedded to Satan", and referring to communism and Nazism as "Gog and Magog"), and his attitude to the Vichy regime quickly hardened into opposition.

He also committed his sister Camille to a hospital in March 1913, where she remained for the last 30 years of her life. Records show that while she did have mental lapses, she was clear-headed while working on her art. Doctors tried to convince the family that she need not be in the institution, but still they kept her there.

Despite sharing in his earlier years in the old-fashioned anti-semitism of conservative France, his response to the radical racialist Nazi version was unequivocal; he had written an open letter to the World Jewish Conference in 1935 condemning the Nuremberg Laws as "abominable and stupid". The sister of his daughter in law had married a Jew, Paul-Louis Weiller, who was arrested by the Vichy government in October 1940. Claudel went to Vichy to intercede for him, to no avail; luckily Weiller managed to escape (with Claudel's assistance, the authorities suspected) and flee to New York. Claudel made known his anger at the Vichy government's anti-Jewish legislation, courageously writing a published letter to the Chief Rabbi, Israel Schwartz, in 1941 to express "the disgust, horror, and indignation that all decent Frenchmen and especially Catholics feel in respect of the injustices, the despoiling, all the ill treatment of which our Jewish compatriots are now the victims... Israel is always the eldest son of the promise [of God], as it is today the eldest son of suffering." The Vichy authorities responded by having Claudel's house searched and keeping him under observation. His support for Charles de Gaulle and the Free French forces culminated in his victory ode addressed to de Gaulle when Paris was liberated in 1944.

Claudel, a conservative of the old school, was clearly not a fascist. The French writers who were attracted by, and collaborated with, the Nazi "New Order" in Europe, much younger men like Céline and Drieu la Rochelle, tended to come from a very different background to Claudel's, nihilists, ex-dadaists, and futurists rather than old-fashioned Catholics (neither of the other two major French Catholic writers, François Mauriac and Georges Bernanos, were supporters of the Nazi occupation or the Vichy regime).

An interesting parallel to Claudel, for Anglophones, is T.S. Eliot, whose later political and religious views were similar to Claudel's. As with Eliot, even those who dislike Claudel's religious and political beliefs, have generally admitted his genius as a writer. The British poet W.H. Auden, at that time a left-leaning agnostic, acknowledged the importance of Paul Claudel in his famous poem "In Memory of W.B. Yeats" (1939). Writing about Yeats, Auden says in lines 52-55:

"Time that with this strange excuse/Pardoned Kipling and his views,/And will pardon Paul Claudel,/Pardons him for writing well." (These lines are from the originally published version; they were excised by Auden in a later revision.)

George Steiner, in The Death of Tragedy, calls him one of the three "masters of drama" in the twentieth century.

Paul Claudel was elected at the Académie française on 4 April 1946.