Born in Minneapolis Engdahl is the son of F. William Engdahl, Sr., and Ruth Aalund (b. Rishoff). Engdahl grew up in Texas, and after a degree in engineering and jurisprudence from Princeton University in 1966 (BA) ,and graduate study in comparative economics at the University of Stockholm from 1969 to 1970, he worked as an economist and free-lance journalist in New York and in Europe.

Engdahl began writing about oil politics with the first oil shock in the early 1970s.

His first book was called "A Century of War: Anglo-American Oil Politics and the New World Order", and discusses the role of Zbigniew Brzezinski and George Ball and of the USA in the 1979 overthrow of the Shah of Iran, which was meant to manipulate oil prices and to stop Soviet expansion. Engdahl claims that Brzezinski and Ball used the Islamic Balkanization model proposed by Dr Bernard Lewis. In 2007, he completed "Seeds of Destruction: The Hidden Agenda of GMO".

Engdahl is also a frequent contributor to the left-wing globalresearch.ca, the main website of the Centre for Research on Globalisation.

William Engdahl has been married since 1987 and has been living for more than two decades, near Frankfurt am Main Germany.

Engdahl stated in 2007 that he had come to believe that petroleum is not biological in origin, produced from remains of prehistoric zooplankton and algae, which had settled to a sea or lake bottom in large quantities under anoxic conditions, which is a theory supported by the majority of petroleum geologists and engineers. Instead he now believes the hypothesis that petroleum is geological in origin, produced deep underground from carbon, by conditions and forces of heat and pressure deeper down than the Earth's bioshpere. Engdahl calls himself an "ex peak oil believer", stating that peak oil is actually a political phenomenon.

Engdahl argued that the Earth is cooling, not warming. He claims that global warming, like peak oil, is merely a "scare" and an attempt "by powerful vested interests to convince the world to sacrifice that they remain in control of the events of this planet".(sic)