Robinhood Markets expects retail investors to become less active in the third quarter.
The online brokerage said in its first earnings report as a public company that frantic trading in crypto currencies had helped more than double its revenue.
A slowdown in retail trading, which has been one of the standout phenomena of the global health crisis-era, comes as the U.S. eased some restrictions in recent weeks.
Robinhood owns the trading app that emerged as the gateway for investors seeking to get in on so-called meme stocks and helped make retail investors a force to be reckoned with.
Robinhood's platform allows users to make unlimited commission-free trades in stocks, exchange-traded funds, options and cryptocurrencies.
Its simple interface made it popular with investors trading from home and contributed to wild rides in shares of companies like GameStop.
Robinhood posted net revenue of $565 million for the quarter compared with $244 million a year earlier - a 131% gain.
But for the upcoming quarter, the firm says it expects "seasonal headwinds and lower trading activity across the industry" to result in lower revenue and fewer new funded accounts.
Another potential area of concern, analysts say, may be the hefty chunk of Robinhood's revenue that comes from investors trading often volatile cryptocurrencies.
Its shares slid as much as 12 percent following the slowdown warning.