He was a comic book and pulp magazine editor, and a science fiction agent and prominent fan. In 1932, Schwartz co-published (with Mort Weisinger and Forrest J. Ackerman) Time Traveller, one of the first science fiction fanzines. Schwartz and Weisinger also founded the Solar Sales Service literary agency (1934–1944) where Schwartz represented such writers as Alfred Bester, Stanley G. Weinbaum, Robert Bloch, Ray Bradbury, and H. P. Lovecraft, including some of Bradbury's first published work and Lovecraft's last. In addition, Schwartz helped organize the first World Science Fiction Convention in 1939. In 1944 he became an editor at All-American Comics, one of the companies that evolved into DC Comics.