Investors should heed Bank of America's warning on bitcoin and other virtual currencies, CNBC's Jim Cramer said Wednesday.

During a post-earnings call Wednesday morning, Bank of America CEO Brian Moynihan responded to a question about cryptocurrencies after the company banned financial advisors from buying bitcoin-related investments for their clients.

"We have limited our relationships," Moynihan said about cryptocurrencies in a media call. "We basically told people they could buy at other accounts, not at Merrill Lynch."

"I think they're right," Cramer said about BofA on "Squawk on the Street." "I mean they have a lot of consumer business that's digital. They'd rather not deal with a currency that's not a currency."

Bitcoin was falling for a second day on Wednesday, breaking below $10,000 for the first time since November. Ethereum and ripple, the second- and third-biggest digital assets, respectively, continued to move lower as well.

"I'm not saying they think it's going to die," said Cramer, host of "Mad Money." "I'm just saying that they think, 'Why the heck do we need this?'"

Later on the call, Moynihan reiterated his worries that cryptocurrencies make it difficult to track fund flows by criminals.

Meanwhile, BofA reported better-than-expected adjusted fourth-quarter earnings earlier Wednesday, but revenue fell slightly short of expectations. Despite not helping customers invest in bitcoin, the bank has applied for patents in blockchain technology.

— CNBC's Evelyn Cheng contributed to this report.