The state oil firm's net loss widened to 36.9bn reais ($10.2bn; Â£7.1bn) in the three months to December.
The company had to write down billions of dollars from assets like oil fields and drilling rigs after crude prices fell by more than 40%.
Petrobras shares fell by nearly 6% in after hours US trading on the results.
Its chief executive said in a press conference that 2015 was "an extremely difficult year for the oil industry".
Petrobras has also been trying to deal with the fallout from an expanding corruption scandal that has gone to the top ranks of government and seen some of its former executives jailed.
On Monday police arrested a man in Portugal they say was laundering payments for two of the jailed Petrobras executives.
Police say the man, Raul Schmidt Felipe Junior, may also have acted as an intermediary between some foreign companies and Petrobras.
Brazil is also mired in its worst recession in a century, which has led to weak demand at home for its fuel products.
To maintain its finances, the firm has drastically reduced its spending and investment plans. Petrobras is also looking to sell some of its assets in order to raise more than $14bn.
Brazil's Petrobras, which is at the centre of a massive corruption scandal, has posted its biggest ever quarterly loss due to the plunge in oil prices.