It was as an editor of fiction that Conklin found his niche, beginning as early as 1930. At the age of 26, while employed as an assistant manager at New York's Doubleday Bookstore, he arranged for the hardcover publication of a story from The Smart Set Magazine (November 1913), reprinting "A Flood" by the Irish writer George Moore in a limited edition of 185 signed copies. Four years later, Conklin and Burton Rascoe published The Smart Set Anthology (1934, reissued as The Bachelor's Companion in 1944), the first collection of stories from that literary magazine.
Conklin's interest in short fiction continued with the 1936 publication of The New Republic Anthology: 1915-1935, edited with Bruce Bliven. The following year, he married Lucy Tempkin on October 1. During the next decade, he wrote books about subways, rental libraries and home construction, in addition to poetry and numerous magazine articles.