Valerie married Eliot, almost 38 years her senior, on 10 January 1957. She is his most important editor and literary executor, having brought to press The Waste Land: Facsimile and Manuscripts of the Original Drafts (1971) and The Letters of T. S. Eliot: Volume 1, 1898-1922 (1989). She also assisted Christopher Ricks with his edition of The Inventions of the March Hare (1996), a volume of Eliot's unpublished verse. A second volume of Eliot's letters, edited by Valerie, had been long-delayed, with much speculation but little solid information as to the reason. In late 2009, however, Volume 2 did come out.

She donates the £15,000 annual prize money for the T. S. Eliot Prize.

Memoir writers who were close companions of T. S. Eliot (such as Joseph Chiari and Herbert Read) have said that Valerie had a rejuvenating effect on Eliot, whose first marriage to Vivienne Haigh-Wood Eliot was stormy; she died after being committed to an asylum. Valerie is credited with giving Eliot some of the happiest years of his life before his health declined. He died on 4 January 1965.