Reuters' Svea Herbst-Bayliss reports that Greenlight lost 3.6% in September, bringing its decline to about 17% for the year.
According to the fund's second-quarter investor update, Greenlight's biggest holdings were Apple, CONSOL Energy, General Motors, gold, Micron Technology and SunEdison.
During the month of September, most of those stocks fell with the exception of GM, which rose about 2%. SunEdison fell more than 30% in the month of September. It's unclear what Einhorn's current position is in those stocks.
Einhorn launched Greenlight Capital in May 1996 with $900,000 from friends and family. Einhorn became famous for a call he made in the spring of 2008 to short Lehman Brothers.
His only previous down year was in 2008, when his fund lost 23%.