PayPal says it will allow customers to buy, sell and hold the cryptocurrency, and rival virtual coins, in its online wallets.
The service will be available to U.S. customers in the coming weeks, and some other countries in the first half of 2021.
From early next year, people will also be able to use the digital currencies at the 26 million merchants on the PayPal network.
Company Chief Executive Dan Schulman says he hopes that will encourage global use of bitcoin and the like.
He says he's working with global central banks on how PayPal can help drive that.
Cryptocurrencies have so far failed to catch on for everyday use.
Their extreme volatility makes them attractive to speculators, but not so much shoppers or merchants.
Companies including payments provider Square and stock trading app Robinhood do already allow users to buy and sell digital coins.
But now PayPal's vast reach could be a game changer.
It has 346 million active accounts worldwide, and processed 222 billion dollars in payments just in the second quarter.
Cryptocurrency transactions on PayPal will be settled in regular currencies, such as the U.S. dollar, meaning merchants won't get paid in virtual coins.