Management also warned revenue growth rates would decelerate in Q3 and Q4.
The social network's stock was down as much as 24% in after-hours trading. In early trading on Thursday, the stock was down by 18%.
For the second quarter, the social network reported earnings-per-share of $1.74 on revenues of $13.23 billion, as well as 2.23 billion monthly active users. Analysts were generally expecting earnings-per-share of $1.72 on revenues of $13.3 billion. They were also expecting 2.25 billion monthly active users for the quarter.
Facebook's monthly active users number was still up 11% year-over-year. Its number of daily active users, 1.47 billion, was also up 11% year-over-year.