The company, an affiliate of Saudi Basic Industries Corp (SABIC) and the first major petrochemicals firm in the kingdom to report earnings, had a net loss of 624.1 million riyals ($166.3 million) in the three months to Dec. 31, it said in a bourse statement.
That compared with a profit of 11.78 million riyals in the same period of 2014.
Kayan cited a drop in the average selling prices of most products as the main reason for the fourth-quarter loss, as well as an impairment on its spare parts inventory.
These factors outweighed the benefits of a drop in feedstock costs, an increase in overall sales volume and a drop in marketing fees from SABIC, it said, without providing sales figures.
Saudi companies issue brief earnings statements early in the reporting period before publishing more detailed results later.
Like many petrochemical firms in the kingdom, Kayan's earnings have been hit hard by falling product prices as they are closely tied to the price of oil, which is languishing at 12-year lows. Saudi producers have also benefited from subsidised energy and feedstock costs, so lower crude prices compress their profit margins.
Kayan's results could have been worse. Maintenance work at some of its plants originally due to take place in October to March 2016 was rescheduled. This had been expected to cost the firm 340 million riyals.
Its 2015 annual loss widened substantially to 1.24 billion riyals, which Kayan blamed on lower product prices as well as a drop in production and sales from maintenance work in February. The company had expected maintenance to cost them 62 million riyals.
It reported a loss of 44.5 million riyals in 2014.
Parent firm SABIC, one of the world's largest petrochemical companies, reports its fourth-quarter earnings on Monday.