Duperreault's career spans 40 years. He was president and chief executive officer of Marsh & McLennan Companies from 2008 to 2012. Before joining Marsh, he served for four years as non-executive chairman of ACE Limited, a global insurance and reinsurance company, CEO of ACE Limited from October 1994 through May 2004, and as the company's president from October 1994 through November 1999.
Prior to joining ACE, Duperreault served in various senior executive positions with AIG and its affiliates from 1973 to 1994.
Duperreault is chairman of Attune, a data-enabled company established by Hamilton Insurance Group, AIG and Two Sigma. He is the chairman emeritus of Blue Marble Microinsurance and former chairman of the board of overseers of the School of Risk Management of St. John’s University, New York.
Duperreault is a member of the boards of the International Insurance Society, IESE Business School, Insurance Information Institute, Bermuda Institute of Ocean Sciences (BIOS), Johnson Controls, and Saint Joseph’s University, Philadelphia, Pennsylvania.
He is credited by the Insurance Hall of Fame with helping to transform Bermuda from an island nation with a small, reinsurance-focused market into a global insurance centre.  He currently resides in Bermuda.
In March 2013, Duperreault was asked by Bermuda's Finance Minister, the Hon. E.T. Richards, to chair the Spending and Government Efficiency (SAGE) Commission. The Commission's primary objective was to make government more efficient, cost-effective, transparent and user-friendly. The SAGE Commission submitted a final report with recommendations on October 31, 2013.
American International Group, Inc., also known as AIG, is an American multinational finance and insurance corporation with operations in more than 80 countries and jurisdictions. As of December 31, 2016, AIG companies employed 56,400 people. The company operates through three core businesses: General Insurance, Life & Retirement, and a standalone technology-enabled subsidiary. General Insurance includes Commercial, Personal Insurance, U.S. and International field operations. Life & Retirement includes Group Retirement, Individual Retirement, Life, and Institutional Markets.
AIG's corporate headquarters are in New York City and the company also has offices around the world. AIG serves 87% of the Fortune Global 500 and 83% of the Forbes 2000. AIG was ranked 60th on the 2018 Fortune 500 list. According to the 2016 Forbes Global 2000 list, AIG is the 87th largest public company in the world. On December 31, 2017, AIG had $65.2 billion in shareholder equity.
AIG was a central player in the financial crisis of 2008. It was bailed out by the federal government for $180 billion, and the government took control. The Financial Crisis Inquiry Commission (FCIC) of the US government concluded AIG failed primarily because it sold massive amounts of insurance without hedging its investment. Its enormous sales of credit default swaps were "made without putting up initial collateral, setting aside capital reserves, or hedging its exposure — a profound failure in corporate governance, particularly its risk-management practices." The US government sold off its shares after the crisis and completed the process in 2012.