The auction house, which has added several new board members after a battle with activist hedge fund manager Dan Loeb, declined to comment on the number of layoffs or other specifics. In a statement to CNBC, Sotheby's said:
"As part of a long-range planning process begun earlier this year, Sotheby's has identified areas for growth and additional investment. To capture these opportunities in an ever-evolving business, the company has decided to reallocate staff and resources. Some departments will be expanded and new positions created, while other areas will see modest staff reductions by the end of the year. Our goal is to build on the strong results we have been achieving, continue to increase our ability to compete in the marketplace, and better serve our clients."
Read MoreSotheby's 2.0: Back in the online auction game
Sotheby's is lagging behind rival Christie's in digital growth and in post-war and Contemporary art, which are driving the top prices in fine art. On Wednesday, Sotheby's announced that auction sales were up 22 percent in the first half of the year and had 47 percent growth in Asia.
Sotheby's said it led the global market in sales of Impressionist and Modern Art, with $931.5 million in sales. The company this week announced a partnership with eBay to stream auctions online and said online bidders competed for 17 percent of lots in 2013.
—By CNBC's Robert Frank