The stock dropped 19 percent to $8.50 after reopening for trading. Shares had been halted pending the news.
BlackBerry had been scheduled to release earnings next week. But the Canadian company said late Friday afternoon it expects a loss of about $950 million to $995 million for the quarter, including a massive inventory charge due to increasing market competition.
The BlackBerry, pioneered in 1999, was the dominant smartphone for on-the-go business people and other customers before Apple debuted the iPhone in 2007. Since then, BlackBerry Ltd. has been hammered by competition from the iPhone as well as Android-based rivals like Samsung.