Untermeyer's first book of poetry, First Love (1911), reflected the influences of Heinrich Heine and British poet Laurence Housman.

For a while, he held Marxist beliefs, writing for magazines such as The Masses, through which he advocated that the United States stay out of World War I.

He was a co-founder, in 1916, of The Seven Arts,[7] a poetry magazine that is credited for introducing many new poets, including Robert Frost, who became Untermeyer's long-term friend and correspondent.

On May 1, 1935, Untermeyer joined the League of American Writers (1935–1943), whose members included Lillian Hellman, Dashiell Hammett, Frank Folsom, Alexander Trachtenberg, I.F.

Goodson-Todman, producer of the show, did not act on the protests against Untermeyer for some time, but finally war veterans began picketing outside the New York City television studio from which What's My Line?

The pressure became too great, and the sponsor Jules Montenier, inventor of Stopette deodorant, said, "After all, I'm paying a lot of money for this.

The last live telecast on which he appeared was on March 11, 1951, and the mystery guest he questioned while blindfolded was Celeste Holm.

that he refused to leave his home in Brooklyn for more than a year,[12] and his wife Bryna answered all incoming phone calls.

[12] Miller was a "very infrequent television watcher" in 1951, according to words he used in his 1987 autobiography,[12] and so he did not notice that Bennett Cerf had replaced Untermeyer on the live TV game show.

He and Bryna Ivens Untermeyer created a number of books for young people, under the Golden Treasury of Children's Literature.