[9] McCarthy's debut novel, The Company She Keeps, received critical acclaim as a succès de scandale, depicting the social milieu of New York intellectuals of the late 1930s with unreserved frankness.

[10] After building a reputation as a satirist and critic, McCarthy enjoyed popular success when the 1963 edition of her novel The Group remained on the New York Times Best Seller list for almost two years.

McCarthy's feud with fellow writer Lillian Hellman formed the basis for the play Imaginary Friends by Nora Ephron.

[11][12] Their feud began in the late 1930s over ideological differences, and was rooted in McCarthy's belief in the innocence of the defendants in the Moscow Trials during the Great Purge and Hellman's unyielding and uncritical support for Soviet Premier Joseph Stalin.

[13] Although McCarthy broke ranks with some of her Partisan Review colleagues when they swerved toward conservative politics after World War II, she carried on lifelong friendships with Dwight Macdonald, Nicola Chiaromonte, Philip Rahv, F. W. Dupee and Elizabeth Hardwick.

Perhaps most prized of all was her close friendship with Hannah Arendt, with whom she maintained a sizable correspondence widely regarded for its intellectual rigor.

[17] In New York, she moved in "fellow-traveling" Communist circles early in the 1930s, but by the latter half of the decade she had sided firmly with the anti-Stalinist Left.

She accordingly expressed solidarity with Leon Trotsky and his followers after the witch hunt targeting them culminated in the Moscow Trials.

[20] Interviewed after her first trip, she declared on British television that there was not a single documented case of the Viet Cong deliberately killing a South Vietnamese woman or child.

She and her brothers, Kevin, Preston and Sheridan, were raised in very unhappy circumstances by her father's Irish Catholic parents in Minneapolis, Minnesota, and under the direct care of an uncle and aunt, whom she remembered for harsh treatment and abuse.

McCarthy explores the complex events of her early life in Minneapolis and her coming-of-age in Seattle in her memoirs, Memories of a Catholic Girlhood and How I Grew.

Her younger brother, Kevin McCarthy, became an actor and starred in such movies as Death of a Salesman (1951) and Invasion of the Body Snatchers (1956).

Under the guardianship of the Prestons, McCarthy studied at the Convent of the Sacred Heart - Forest Ridge in Seattle and Annie Wright Seminary in Tacoma.