"It's saved our family," Armstrong told CNBC in an interview that aired on Thursday.
Armstrong said in the interview he was not aware that he was investing in Uber, which at the time was worth $3.7 million, when he gave money to venture capitalist Chris Sacca of Lowercase Capital.
Uber, which is preparing to go public next year, could be valued at $120 billion according to proposals made by U.S. banks bidding to run the offering.
Armstrong did not disclose how much his investment in Uber is currently worth, saying "it's a lot more" and "it's too good to be true".
When asked by the interviewer if he had made "10, 20, 30, 40 or $50 million", Armstrong replied: "It's one of those. It's a lot, it's a lot."
Armstrong won the Tour de France a record seven times but was stripped of his titles and banned for life in 2012 by the U.S. Anti-Doping Agency after it accused him of engineering one of the most sophisticated doping schemes in sports.
The American later admitted to the cheating in a January 2013 televised interview with Oprah Winfrey.
(Reporting by Frank Pingue in Toronto, editing by Nick Mulvenney)
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