Khashoggi headed a company called Triad International Holding Company which among other things built the Triad Center in Salt Lake City, which later went bankrupt. He was famed as an arms dealer, brokering deals between US firms and the Saudi government, most actively in the 1960s and 1970s. In the documentary series The Mayfair Set, Saudi author Said Aburish states that one of Khashoggi’s first weapons deals was providing David Stirling with weapons for a covert mission in Yemen during the Aden Emergency in 1963. Among his overseas clients were defense contractors Lockheed Corporation (now Lockheed Martin Corporation), Raytheon, Grumman Aircraft Engineering Corporation and Northrop Corporation (the last two of which have now merged into Northrop Grumman).

In the 1960s, Khashoggi married 20-year-old Englishwoman Sandra Daly who converted to Islam and took the name Soraya Khashoggi. They raised one daughter (Nabila) and four sons together (Mohamed, Khalid, Hussein, and Omar). Another daughter, Petrina, was born after the couple divorced in 1974.

Khashoggi also appeared in Lifestyles of the Rich and Famous in 1985 with host Robin Leach which showcased Khashoggi’s extravagant lifestyle.

In the 1980s, the Khashoggi family occupied one of the largest villa estates in Marbella, Spain, called Baraka, hosting lavish parties. Guests at these parties included film stars, pop celebrities and politicians. In 1985, celebrity reporter Robin Leach reported Khashoggi threw a five-day birthday party in Vienna for his eldest son, and in his heyday, Khashoggi spent $250,000 a day to maintain his lifestyle. He continued to spend lavishly even when he encountered financial problems. His net worth was said to have been down to about 8 million in 1990. Due to his extravagant lifestyle, he was called the Great Gatsby of the Middle East.

In 1988, Khashoggi was arrested in Switzerland, accused of concealing funds, and held for three months. Khashoggi stopped fighting extradition when the U.S. prosecutors reduced the charges to obstruction of justice and mail fraud and dropped the more serious charges of racketeering and conspiracy. In 1990, a United States federal jury in Manhattan acquitted Khashoggi and Imelda Marcos, widow of the exiled Philippine President Ferdinand Marcos, of racketeering and fraud.

Khashoggi was implicated in the Iran–Contra affair as a key middleman in the arms-for-hostages exchange along with Iranian arms dealer Manucher Ghorbanifar and, in a complex series of events, was found to have borrowed money for these arms purchases from the Bank of Credit and Commerce International (BCCI) with Saudi and United States backing. His role in the affair created a related controversy when Khashoggi donated millions to the American University in Washington, DC to build a sports arena which would bear his name. Khashoggi was a member of the university’s board of trustees from 1983 until his indictment on fraud and other charges in May 1989. Khashoggi was “principal foreign agent” of the United States and helped establish the supranational intelligence partnership known as the Safari Club.

In 1991 Khashoggi made an extended appearance on the British television programme After Dark, alongside, among others, former Prime Minister Edward Heath and Lord Weidenfeld.

In January 2003, Seymour Hersh reported in The New Yorker magazine that former U.S. Assistant Secretary of Defense Richard Perle had a meeting with Khashoggi in Marseille in order to use him as a conduit between Trireme Partners, a private venture capital company of which he was one of three principals, and the Saudi government. At the time, Perle was chair of the Defense Policy Board Advisory Committee, a Defense Department advisory group, which provided him with access to classified information and a position to influence defense policy.

Khashoggi was a financier behind Genesis Intermedia, Inc. (formerly NASDAQ: GENI), a publicly traded Internet company based in the US. In 2006, Khashoggi was sued by the U.S. Securities and Exchange Commission for securities fraud. The case was dismissed in 2008 and Khashoggi did not admit or deny the allegations.

Khashoggi died on 6 June 2017 while being treated for Parkinson’s disease at the St Thomas’ Hospital in London. He was 81.