Son of a Liverpool jeweler, he was born in the UK. Not wishing to follow his father's career, he began to travel around the Mediterranean. While on vacation in Barcelona, he was witness to the outbreak of the Spanish Civil War, a conflict that he covered as correspondent for the United Press agency. Initially a supporter, however not militant, of the Communist Party, he became disappointed with it during the course of the war, eventually coming to the conclusion that the Communists had betrayed the Republic. After the war he moved to Mexico and spent several years there with his first wife, Gladys Evie Green, interviewing refugees of the conflict and putting together material about the war. This material is now held at the Hoover Institute of Stanford University.
After separating from his wife, in 1949 he immigrated to the United States, settling in Sunnyvale, California. For many years he worked as an historian and a real estate broker. He died of prostate cancer in November 1987.
He wrote three volumes about the Spanish Civil War:
- The Grand Camouflage. The Communist conspiracy in the Spanish Civil War, published in 1961;
- The Spanish Revolution, published in 1979;
- The Spanish Civil War: Revolution and Counterrevolution, published in 1991.
Bolloten's work had a great influence on other North American Hispanists like Stanley G. Payne as well as on the historiography of the war in Spain itself. His research on the revolution of 1936 has been followed by a good number of specialists in this period of Spanish history.