The company was founded in 1974 by Stuart Wheeler as a spread betting business under the name IG Index (an abbreviation for Investors Gold Index) which allowed people to trade gold prices as an index instead of buying the physical commodity. In July 2000, shares in the newly named IG Group plc were first listed on the London Stock Exchange.
In July 2002, IG Group commenced trading in Australia after a change in the country's financial services legislation made it possible to offer contracts for difference to Australian residents. IG Group took the opportunity to acquire its founder's shares, and those of certain other long-standing shareholders, in a management buy-out (backed by private equity firm CVC Capital Partners) which valued the company at £143 million; IG Group plc's listing on the London Stock Exchange was subsequently cancelled on 7 November 2003.
In May 2005, after two years of private ownership, IG Group and CVC Capital Partners re-floated the company on the main list of the London Stock Exchange with a valuation of £393 million. In October 2008, IG Group acquired FXOnline Japan KK, a Japanese retail FX business. IG Group has been trying to gain access to the potentially lucrative US market where IG Group's main products, contracts for difference and financial spread betting, are currently not legal. In 2007, it purchased HedgeStreet, a small US based company that developed an electronic marketplace that allows online retail investors to trade financial derivatives. It renamed this the North American Derivatives Exchange or (NADEX) and has been attempting to use this to develop a product that looks like its binary option "digital 100s" product but that meets the US financial regulations and can be offered to retail traders. In May 2010, it obtained permission from the US Commodity Futures Trading Commission to make various technical changes that move in that direction.
In June 2011, IG Markets shut down its traditional fixed-odds sports service extrabet, which had an emphasis on in-play betting. The fixed odds sport service was shut down to focus on financial wagers, after failing to find a buyer for the whole unit. In September 2014, the company started its own online stockbroking platform offering prices on some 4,500 stocks.
In January 2015, the Swiss National Bank announced that it would be discontinuing its minimum exchange rate policy. In October 2015, IG "accepted a ruling by the UK’s Financial Ombudsman Service that it should compensate some customers that lost money during a rapid appreciation of the Swiss franc in January". Peter Hetherington was appointed CEO in December 2015 when Tim Howkins retired after nine years in charge. In September 2016, IG Group acquired DailyFX, a foreign exchange trading news and research portal, from FXCM for $40 million.