McClintic was born in Seattle, attended Washington University in St. Louis and New York's American Academy of Dramatic Arts, and became an actor, but soon became a stage manager and casting director for major Broadway producer Winthrop Ames.

McClintic's first major success was on The Barretts of Wimpole Street featuring his wife, the American actress Katharine Cornell, in 1931.

Katharine Cornell served on the Board of Directors of The Rehearsal Club, a place where young actresses could stay while looking for work in the theatre.

He directed every play that Cornell starred in, including Romeo and Juliet, Candida, Antony and Cleopatra, No Time for Comedy, Antigone, Saint Joan, The Doctor's Dilemma, Three Sisters, and There Shall Be No Night, and The Constant Wife.

Their production company brought over many of the leading Shakespearean actors of the day, giving them their first prominent Broadway roles, including John Gielgud, Ralph Richardson, Maurice Evans, and Laurence Olivier.