Investors sent the stock down 11 per cent in after-hours trading.
Netflix still boasts some 150 million subscribers globally and remains the service of first resort for many consumers. But the prospect of a subscriber slowdown is compounded by the launch of new services, including Disney+ in the fall and HBO Max next year, competing for viewers' dollars.
In an investor letter, Netflix explained the bleak numbers as part of a "pull-forward" effect from the first quarter, when subscriber additions nearly totaled 10 million worldwide.
The streamer also saw lower subscriber figures in the second quarter last July, which is attributed to seasonality and expected a bounceback in future quarters, which largely happened.
But the coming months could be trickier. WarnerMedia recently decided against renewing its deal for Netflix to air "Friends" as it prepares to launch its own service, and NBC Universal is doing the same for "The Office." Both shows are very popular, and their departure could lead, investors fear, to mass subscriber exits.
Netflix has been ramping up its original content to combat these departures and keep its service a must-have. Executives in the letter pointed to the debut this month of the new season of "Stranger Things," which according to Nielsen garnered 26.4 million viewers in its first four days of release.
In a note last week, Wedbush Securities analyst Michael Pachte said that despite the popularity of these originals, it "is unclear whether Netflix can replace it with quantity and quality sufficient to keep its current subscriber base loyal."