BMW said net profit plunged by 73.8 percent from the third quarter of 2008 to €78 million ($115 million).
In the first nine months of the year, net profit lost a massive 96.4 percent from the same period a year earlier to €47 million, the group said.
Analysts polled by Dow Jones Newswires had forecast third quarter profit of €94 million, and the results underscored the global downturn's effect on manufacturers of high-end automobiles.
Small car makers have done better owing to government car scrapping schemes and other fiscal incentives, and BMW's poor figures stood in contrast to those from groups such as Fiat and Ford.
Daimler on the other hand, which makes Mercedes-Benz autos, was also hit by a slump in the luxury car market, and reported last week a 74 percent drop in third quarter net profit to €56 million.
Despite signs of improvement, particularly in China which is now the group's largest Asian market, "the BMW Group only expects the situation to stabilise at a low level during the last quarter of 2009," it said in a statement.
BMW forecast that full-year unit sales would be between 10-15 percent lower than in 2008.
"For the time being at least, it cannot be assumed that an enduring recovery has taken hold," the statement said.
Core earnings before interest and tax (EBIT) were also sharply lower, shedding 85.8 percent to €55 million in the three-month period, while sales edged down to €11.76 billion from €12.6 billion.
BMW nonetheless said that it aimed for a full year profit, following "some early signs of recovery, particularly in August and September."
Unit sales of BMW, MINI and Rolls-Royce brand autos were 7.2 percent lower at 324,100 in the third quarter, and 15.7 percent lower at 939,554 for the first nine months of the year.
Investors shunned BMW shares, and they lost 6.17 percent to €31.53 in morning trading on the Frankfurt stock exchange, while the DAX index of German blue-chips was 1.43 percent lower overall.
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A trader was quoted by Dow Jones as saying that the third quarter earnings were bad when compared with those of Daimler.
"It's clear that BMW isn't a brand which profited from the cash for clunkers scheme," so the earnings at BMW reflect the "true situation" for the auto industry, the trader said.
The auto sector has begun to hear better news elsewhere however, with Ford posting surprise quarterly earnings of nearly a billion dollars and saying it was on track to become "solidly profitable" by 2011 after years of losses.
Fiat said last month that it had made a slight profit of €25 million in the third quarter following two consecutive quarterly losses, and that it expected market conditions to improve by the end of the year.