Jonas was born in Budapest, the son of Dr. Georg M. Hübsch and Magda Hübsch (née Klug). During the Holocaust in Hungary in 1944—45, Jonas went into hiding with his family. He emigrated to Canada in 1956.

Jonas was married to Barbara Amiel from 1974 to 1979, and they remain good friends. A book he co-wrote with Amiel, By Persons Unknown: The Strange Death of Christine Demeter, won a 1978 Edgar Allan Poe Award for Best Fact Crime book. Although Jonas is of Jewish descent, his parents and grandparents converted to Christianity when he was three years old. Jonas writes in his memoirs that Amiel insisted on being married in a synagogue, which was the first time Jonas had been inside one.

Jonas worked as a radio producer in Budapest before escaping after the 1956 Hungarian Revolution. He worked for the Canadian Broadcasting Corporation from 1962 to 1985 as a script editor and producer.

He worked as a columnist for the Toronto Sun from 1981 to 2001, when he moved to the National Post where he remains a regular contributor. He has written 15 books, one play, and two operas.

Vengeance

His 1984 book Vengeance, describing the events of Operation Wrath of God became the basis for two films: TV-film Sword of Gideon (1986), and feature film Munich (2005), directed by Steven Spielberg. Jonas has complained of what he considers pro-Palestinian distortions in Munich. Specifically, Jonas feels that the script writer Tony Kushner, a Jew who has referred to the formation of Israel as a "mistake," failed to make a moral distinction between terrorism and legitimate military actions. At the same time, some critics claim that Jonas's source for the book, New York security consultant Juval Aviv, who claimed to be the head of a Mossad hit team, had fabricated the story. In a lengthy article in Macleans magazine in January 2006, Jonas admits that there is no way of determining whether his source was telling the truth. However, Jonas did attempt to verify many details of the story by visiting the places in Europe where his source claimed to be operating, and at least to that extent he is satisfied with the evidence.