In 1919, he began a career as a reporter with a weekly newspaper in his hometown of New York called The Crisis. He was an editor at the Crisis from 1919 to 1924 and met his future wife there, Nina Hammon. Nina bore him three children: Jeanette (1921), who died at the age of six months; Mary (1923), who eventually changed her last name to Hennings; and George (1924).
From 1924 to 1929, Nathan worked as an executive at the American Newspaper Publishers Association. During this period, he learned that he had diabetes and suffered from hypoglycemia. He became professional freelance writer after leaving the AMPA in 1929.
He began writing for magazines such as Esquire and The American Mercury. During the 1930s, Nathan wrote for many publications including Collier's Weekly, The Saturday Evening Post, Cosmopolitan Magazine, The Ladies' Home Journal , Liberty Magazine , Woman's Home Companion , The American Weekly , Vogue , Town & Country , Redbook , McCall's Magazine , Liberty Magazine , Collier's Weekly , Woman's Day , Parents Magazine , Ladies' Home Journal , Good Housekeeping , Redbook , Redbook Reader's Digest Annual . He also wrote articles for various government publications like Town & Country Magazine .
He also wrote plays and screenplays including "The Red House" (1934) with Ruth Chatterton; "The Road Back" (1935) with Loretta Young; "The Conqueror" (1936), which starred John Wayne; "The Sea Hawk" (1940); "Oklahoma" (1943) starring Katharine Hepburn; "Seventh Heaven" starring Gene Tierney; "So Ends Our Night" (1945) with Joan Fontaine; "I'll Cry Tomorrow" with Elizabeth Taylor; "The Dark Corner" with Robert Mitchum; "Call Northside 777" starring James Cagney; "Two Years Before the Mast" with Humphrey Bogart; "Desperate Journey" with Robert Taylor.
His prolific writing career also included screenplays for