Earnings before interest, taxes, depreciation and amortization (EBITDA) rose to 15.6 billion reais from 13 billion.
The oil giant had been expected to post a net profit of 9.3 billion reais and EBITDA of 17 billion reais, according to the average forecast of five analysts surveyed by Reuters.
Petrobras said its oil and gas output worldwide rose to 2.44 million barrels of oil equivalent per day in the third quarter from 2.31 million BOE/day a year earlier.
Natural gas output in Brazil grew 22 percent.
Petrobras attributed the increase in output to new wells connected to the P-52 and P-54 platforms in the Roncador field and the ESS-103 well in the subsalt layer in the Campos basin that is connected to the P-34 platform.
The average price of benchmark Brent oil in the three months ending in September was $115 per barrel compared with $75 a year earlier, Petrobras said.
The average price was $121 a barrel in the second quarter but the third semester showed better financial results.
The company posted gains of 2.8 billion reais from financial operations influenced by the sharp depreciation of Brazil's currency, the real, over the three months.
"The profits were influenced by the exchange rate,'' said Almir Barbassa, head of finance at Petrobras.
In the same quarter of 2007 and in the second quarter of 2008, Petrobras posted losses of 1.1 billion reais and 1.8 billion reais respectively in its financial operations.
The real depreciated sharply against the dollar in the third quarter.