"With all the talk about bitcoin, a good deal of people are also starting to open accounts where they can buy and sell crypto-currencies," Bespoke Investment Group said in a Friday blog post.
Schwab reported in mid-November it had 10.6 million active brokerage accounts in October, up 5 percent from the same period last year.
In contrast, Coinbase had 11.7 million users at the end of October, according to data compiled by Alistair Milne, co-founder and chief investment officer of Altana Digital Currency Fund. That's up 148 percent from 4.7 million a year ago.
Through Sunday, that number had grown to 13.3 million, according to Milne's data. That was after an increase of 300,000 users in the last week alone.
Coinbase is the leading platform through which Americans buy digital currencies bitcoin, ethereum and litecoin. Schwab is the second largest broker-dealer by assets under management, according to Investopedia. Fidelity ranks first.
A representative from Schwab did not immediately respond to a phone call and emailed request for comment.