Many of Beauvoir's works deal with her own experiences, sometimes concealed in fictional terms, sometimes revealed in her autobiography. This is how, in Memoirs of a Dutiful Daughter, we learn of her growing up in a bourgeois Parisian family. Her childhood and adolescence seem to have been quite happy although she does not share any intimate details, only that she commanded her younger sister Helène (called Poupette) and her other playmates. Her attachment to Elizabeth Le Coin--called Zaza in her memoirs--set a pattern for the many important friendships with women Beauvoir would maintain throughout her life.

Beauvoir excelled in school, and her father at first supported her intellectual aspirations. Later he resented her success, and Beauvoir eventually began to rebel against the constraints of her bourgeois upbringing. She also rejected her mother's Catholicism. Her parents expected Beauvoir to get married as other girls from her social class did, but she insisted on attending university and becoming a teacher so that she would be able to support herself. While preparing for her final examinations, she met Jean-Paul Sartre and associated with his friends, a group of young philosophers who appreciated Beauvoir's specialization on Leibniz. As Toril Moi points out, Beauvoir was "a pioneering woman in her own time" when, as only the ninth woman and the youngest student ever, she completed the impressive final examination in philosophy. She passed the exam with flying colors and took second place to Sartre. Her professors admitted that they arrived at this final ranking only with great difficulty. After graduation, Beauvoir began a teaching career at various lycées, where she was much admired by her students for her unconventional approach and fascinating lectures. She, thus, established her professional independence by working outside the home. All her life she cherished her individuality and travelled extensively.

While the extent of her impact on contemporary women may be disputed, Beauvoir, nonetheless, managed to model the persona of a successful, professional woman writer. She also believed that such work constituted a valid alternative to motherhood. Beauvoir's writing was first published during the 1940s and elaborated her philosophical ideas in fictional form. Otherwise uninvolved in the political events of the day, in Letters to Sartre she describes, in detail, the German Occupation and displays her fears for Sartre's safety during his internment as a prisoner-of-war in Germany. It was only after the war that her thinking became more politicized.

In The Ethics of Ambiguity, Beauvoir would clarify various points of Sartre's existentialism for a post-war world. As Kate and Edward Fullbrook argue in Simone de Beauvoir and Jean-Paul Sartre: The Remaking of a 20th-Century Legend (1994), Sartre may actually have been influenced by Beauvoir's ideas before he formulated his philosophy. Soon after the war, Beauvoir also went on a long lecture tour of the United States where she met the novelist Nelson Algren, with whom she had a long-distance relationship for nearly 15 years. Both Beauvoir and Sartre, despite their lifelong "essential" relationship, continued to see other people in "contingent" relationships, because they rejected marriage as an outdated and oppressive bourgeois institution.

Her long novel, The Mandarins--usually considered a key to understanding the leftist intelligentsia's experience of the postwar years--features characters reminiscent of Beauvoir, Sartre, Algren, and Albert Camus. In great detail, Beauvoir describes how various characters try to reconfigure their lives and relationships after the war. Focusing on two characters, Henri Perron and Anne Dubreuilh, Beauvoir alternates their accounts of the events, letting them overlap at times and, thus, affording the reader two perspectives of the same incident. Despite some stylistic flaws, the novel received the Prix Goncourt because of its philosophical depth and political and historical significance.

Despite her literary success, Beauvoir suddenly became aware of her situation as a woman in a male world and decided to explore this idea in The Second Sex. The study employs existentialist philosophy and an historical approach in an effort to explain women's secondary social status. Man sees woman as "a sexual being" and imposes many of his ideas and dreams on his image of woman, making her his other. Beauvoir explains that woman "is defined and differentiated with reference to man and not he with reference to her." Thus, all women, become "The Second Sex."

She traces this evolution from prehistory and classical antiquity, through the Middle Ages and the Enlightenment into our own time. Particularly interesting are her insights into mythology and her close analysis of images of women in the works of Montherlant, D. H. Lawrence, Claudel, Breton, and Stendhal. The work's greatest significance rests on the premise that woman is not biologically predetermined to become mother and wife but free to determine her own fate. Contemporary critics point to flaws in Beauvoir's argument: hasty generalization resulting from insufficient and dated evidence, for instance. They also deplore her negative attitude toward the female body and motherhood. Furthermore, many have deemed her whole approach Eurocentric and phallocentric. Although Beauvoir had previously described women in her novels, The Second Sex marked a turning point in her writing career: The Woman Destroyed and Les Belles Images would discuss women's issue even more overtly. Until her death in 1986, Beauvoir continued her political and philosophical pursuits. A lifelong opponent of colonialism, she supported the independence of both French Indochina and Algeria. In Djamila Boupacha (1962), she exposed the torture of an Algerian girl by the French military. The Long March is a detailed account of Communist China in the late 1950s. Several of her last works discussed the impact of old age and death.