LinkedIn shares dropped 26% after the company projected lower than expected profits for the first quarter of 2016, blaming shaky global economic conditions.
The company, which operates the world’s largest online network for professionals, forecast earnings of $0.55 per share – far below analysts expectations of $0.74 per share.
LinkedIn also reported a loss of $8m (£5.4m) for the year, compared with a $3m profit in 2014.
LinkedIn has been investing heavily in expansion outside the US, and said it plans to continue those efforts.
Ad revenue growth also slowed, rising 20% in the fourth quarter. This was the slowest rise for the company in over two years, as competition from ads offered by Google increased.
Finance director Steve Sordello said the business – which connects recruiters and job-seekers – was facing pressure in Europe, the Middle East, Africa and the Far East due to “current global economic conditions”.
LinkedIn has been spending heavily on expansion by buying firms, hiring sales staff and growing in China and other markets outside the US.
It is phasing out an online ad product called Lead Accelerator in the first half of 2016 which it said would hurt revenue by at least $50m (£34m) this year – after it “required more resources than anticipated”.