Samsung Electronics, the world’s biggest maker of mobile phones and TVs, has forecast a fall in profit for the October-to-December quarter.
It expects to make an operating profit of 8.3 trillion won ($7.8bn; £4.8bn) for the quarter, down 18% from the previous three months.
Compared with the same period in the previous year, it is a 6% decline.
Samsung did not say what caused the dip, but analysts said falling profit margins for smartphones had hurt it.
“As the growth in the smartphone sector matures, and vendors seek expansion in emerging economies, both prices and operating margins have been coming down,” Manoj Menon, managing director of consulting firm Frost & Sullivan, told the BBC.
Mr Menon added that profit margins of smartphone makers were likely to “remain under pressure” in the coming months.
Samsung has enjoyed robust growth in recent years, fuelled in part by the success of its smartphone division.
The success of its Galaxy range of smartphones saw the South Korean firm displace Nokia as the world’s biggest phone maker in 2012.
However, competition in the sector has increased with other phone makers launching new products.