KenolKobil added earnings for the first six months ended June were hit by foreign exchange losses as well as lower margins from oil trading and distribution.
KenolKobil said that high oil prices, price controls, volatile exchange rates in the countries they operate in and high financing costs had continued to undermine its net profit.
"As a result, management expects that the company's results for the second six months ending December 31 2012 to be much lower than the results for the same period ending December 31 2011," it said in a statement.
The oil marketer posted a first-half pretax loss of 5.68 billion shillings having made a profit in the same period last year of 3.23 billion shillings.
KenolKobil, which is one of the largest fuel marketing firms in the east African country also operates in eight neighbouring nations including Uganda, Burundi, Tanzania, Rwanda and Zambia.
Last week it said takeover talks with Switzerland-based Puma had collapsed.
At 1016 GMT, its share price was down 1.4 percent to 11 shillings.