Icahn, who spoke with CNBC's "Fast Money: Halftime Report," said that Saudi Arabia's decision not to cut oil production blindsided the global market, and that he expects the commodity's price will keep sliding.
"I think [oil's price] will continue to go down unless there is some outside event," Icahn said.
Still, he said he sees a "tremendous opportunity" for when oil eventually rises again—but he admitted that nobody knows when that will happen.
"I wouldn't rush in now on oil, and that's talking against myself because I own a lot of oil stocks," he added.
Icahn did allow, however, that "there will be increased demand for oil over the years," and easily obtainable resources are dwindling, so companies engaged in offshore production will continue to gain importance. Icahn is one of the largest shareholders in drilling firm Transocean.