Shares tumbled 21 percent to $200.24 at 2:15 p.m. in New York.
Second-quarter revenue will be $670 million to $675 million, the Mountain View, California-based company said late yesterday. Analysts had predicted $718.3 million, on average, according to Capital IQ data.
LinkedIn also slashed its forecast for annual revenue to $2.9 billion, from $2.93 billion to $2.95 billion.
LinkedIn blamed the weak outlook on changes in foreign exchange rates and the pending $1.5 billion acquisition of Lynda.com.
The company expects revenue contribution from Lynda to be delayed as it works its way to complete the integration.
Chief financial officer Steve Sordello said he expected revenue contribution from the acquisition to "normalize" in the second half of 2016.
For the first quarter, the company reported net loss widened to $42.5 million, or 34 cents per share, from $13.4 million, or $0.11 per share, a year earlier. Excluding items, the company earned $0.57 per share.
Revenue rose to $637.7 million from $473.2 million.
Revenue growth from the company's hiring business slowed to 36 percent for the first quarter. The business, which the company calls Talent Solutions, accounted for about 62 percent of total revenue.
"Q1 was a solid quarter in which we made meaningful progress against our multi-year strategic roadmap," chief executive officer Jeff Weiner said in the statement. "During the quarter, we maintained steady growth in member engagement while achieving strong financial results."