Lewis, 86, was charged with giving his friends, personal assistants, romantic partners, and private pilots insider information about his businesses.
According to US officials, millions of dollars were made from the scam.
Lewis entered a plea agreement with prosecutors in which he admitted guilt to two counts of securities fraud and conspiracy.
Lewis established the Tavistock Group, an investment firm with holdings in a wide range of real estate, sports, financial, energy, and life sciences businesses.
With an estimated net worth of more than £5 billion ($6.4 billion), he was placed 39th on the Sunday Times Rich List for 2023.
Thirteen counts of conspiracy and sixteen counts of securities fraud were brought against him after his arrest in July 2023.
The prosecution claimed that he misused his access to company board rooms between 2013 and 2021 and gave his contacts insider information.
US attorney Damian Williams said those contacts made millions of dollars in “sure thing” bets on the stock market.
In one case, Lewis allegedly advised a girlfriend to invest in a biotech business in July 2019 before the company’s clinical trial results were disclosed. This is according to the indictment.
After that, it is said that he personally accessed her bank account and invested $700,000 to make an eventual profit of $849,000.
In a separate incident, Lewis is accused of providing his private pilots, Patrick O’Connor and Bryan Waugh, with confidential information and then wiring them $500,000 each to purchase stock in a company.
“Boss lent Marty and I $500,000 each for this,” and “the Boss has inside info… otherwise why would he make us invest,” are two alleged texts that Mr. O’Connor sent to a friend after the loan.
