In 1924, Chambers read Vladimir Lenin's Soviets at Work and was deeply affected by it. He now saw the dysfunctional nature of his family, he would write, as "in miniature the whole crisis of the middle class"; a malaise from which Communism promised liberation. Chambers's biographer Sam Tanenhaus wrote that Lenin's authoritarianism was "precisely what attracts Chambers... He had at last found his church"; that is, he became a Marxist. In 1925, Chambers joined the Communist Party of the United States (CPUSA) (then known as the Workers Party of America). Chambers wrote and edited for Communist publications, including The Daily Worker newspaper and The New Masses magazine. Chambers combined his literary talents with his devotion to Communism, writing four short stories in 1931 about proletarian hardship and revolt, including Can You Make Out Their Voices?, considered by critics as one of the best fiction from the American Communist movement. Hallie Flanagan co-adapted and produced it as a play entitled Can You Hear Their Voices? (see Writings by Chambers, below), staged across America and in many other countries. Chambers also worked as a translator during this period; among his works was the English version of Felix Salten's 1923 novel Bambi, A Life in the Woods.
Chambers was recruited to join the "Communist underground" and began his career as a spy, working for a GRU apparatus headed by Alexander Ulanovsky (aka Ulrich). Later, his main controller in the underground was Josef Peters (whom CPUSA General Secretary Earl Browder later replaced with Rudy Baker). Chambers claimed Peters introduced him to Harold Ware (although he later denied he had ever been introduced to Ware), and that he was head of a Communist underground cell in Washington that reportedly included:
- Henry Collins, employed at the National Recovery Administration and later the Agricultural Adjustment Administration (AAA).
- Lee Pressman, assistant general counsel of the AAA.
- Alger Hiss, attorney for the AAA and the Nye Committee; he moved to the Department of State in 1936, where he became an increasingly prominent figure.
- John Abt, chief of Litigation for the AAA from 1933 to 1935, assistant general counsel of the Works Progress Administration in 1935, chief counsel on Senator Robert La Follette, Jr.'s LaFollette Committee from 1936 to 1937 and special assistant to the United States Attorney General, 1937 and 1938.
- Charles Kramer, employed at the Department of Labor National Labor Relations Board (NLRB).
- Nathan Witt, employed at the AAA; later moved to the NLRB.
- George Silverman, employed at the Railroad Retirement Board; later worked with the Federal Coordinator of Transport, the United States Tariff Commission and the Labor Advisory Board of the National Recovery Administration.
- Marion Bachrach, sister of John Abt; office manager to Representative John Bernard of the Minnesota Farmer-Labor Party.
- John Herrmann, author; assistant to Harold Ware; employed at the AAA; courier and document photographer for the Ware group; introduced Chambers to Hiss.
- Nathaniel Weyl, author; would later defect from Communism himself and give evidence against party members.
- Donald Hiss, brother to Alger Hiss; employed at the Department of State.
- Victor Perlo, chief of the Aviation Section of the War Production Board, later joined the Office of Price Administration Department of Commerce and the Division of Monetary Research at the Department of Treasury.
Apart from Marion Bachrach, these people were all members of Franklin D. Roosevelt's New Deal administration. Chambers worked in Washington as an organizer among Communists in the city and as a courier between New York and Washington for stolen documents which were delivered to Boris Bykov, the GRU station chief.
Other covert sources
Using the codename "Karl" or "Carl", Chambers served during the mid-1930s as a courier between various covert sources and Soviet intelligence. In addition to the Ware group mentioned above, other sources that Chambers dealt with allegedly included:
- Noel Field, employed at the Department of State.
- Harold Glasser, Assistant Director, Division of Monetary Research, United States Department of the Treasury.
- Ward Pigman, employed at the National Bureau of Standards; Labor and Public Welfare Committee.
- Vincent Reno, a mathematician at the U.S. Army Aberdeen Proving Ground.
- Julian Wadleigh, economist with the Department of Agriculture and later the Trade Agreements section of the United States Department of State.
- Harry Dexter White, Director of the Division of Monetary Research at the Secretary of the Treasury.