"I think the public is walking into a trap again as they did in 2007," the activist investor told CNBC's "Fast Money Halftime Report." "I think it's almost the duty of well-respected investors, like myself I hope, to warn people, to tell people, that really you are making errors."
Icahn compared the current market situation to the prerecession days, when mortgage-backed securities were being widely sold. "It's almost deja vu," he said. Many companies are selling at huge multiples and reporting earnings that are "sort of fudged" due to various accounting methods, he said.
"I do think you are going to have a dramatic pullback, certain things may happen," he said. To remedy this, Icahn would like to see the government and regulators look at the way earnings and guidance are reported by companies.
The chairman of Icahn Enterprises said he doesn't understand why someone would buy a high-yielding bond that is significantly riskier than a corporate bond, which could bring in 3 percent over seven years.
"Even if the Fed starts raising rates, those high yields are very suspect now," he said, because who is going to buy them?
Meanwhile, Icahn said that the economy is picking up, though "I'm not sure how much of that is artificial because of low interest rates."
"The longer you wait to take the patient off the medicine, the harder it will be to curtail inflation, and it [inflation] will come," he warned.
Earlier on Wednesday, Icahn said his firm sold off its remaining stake in Netflix, a day after it announced a 7-for-1 stock split. He said Apple "currently represents [the] same opportunity we stated [Netflix] offered several years ago."
Read More Carl Icahn sells last of Netflix shares
This isn't the first time Icahn has warned about the markets. Last October, he cautioned that the high-yield market is in a bubble and that he was ''quite concerned that something is going to happen'' to the stock market.
—CNBC's Everett Rosenfeld contributed to this report.