Petronas is the single largest source of Malaysian government revenue and of national export earnings.
The unlisted firm, Malaysia's only Fortune 500 company, posted a 4.6 billion ringgit ($1.14 billion) net profit for the first quarter compared to 11.4 billion ringgit during the same period last year.
Revenue fell by 26 percent to 49.1 billion.
The firm said in a statement it expects a continued impact from volatile oil prices and the foreign exchange rate.
In March Petronas announced cuts in capital and operating spending of 50 billion ringgit over the next four years, starting with 15-20 billion this year.
Sinking prices of oil and other commodities have battered Malaysia's growth prospects.
The economy expanded 4.2 percent year-on-year in January-March, its slowest rate since the global financial crisis.