Santa Monica online matchmaker eHarmony said that Chief Executive Greg Waldorf has abruptly stepped down, and the chief operating officer is taking over until a replacement can be found.

Waldorf was the company’s founding investor in 2000 and had been CEO since 2006. In addition to leaving his management role, Waldorf, 42, also resigned from the board. COO Greg Steiner, who also is president, will run the company as the board conducts a CEO search, eHarmony said late Tuesday.

“As eHarmony begins its second decade, the time is right for me to step down,” Waldorf said in a statement. “I’m confident that the team will continue to deliver on its promise to eHarmony members who entrust us to help them find the love of their lives.”

Neither eHarmony nor Waldorf said why he decided to step down, but the company praised his tenure at the company. It did not say whether he still has an ownership position in the private company.

“Without Greg’s involvement, eHarmony never would have happened. From before our beginnings he guided us all along the way,” Chairman Neil Clark Warren said in a statement. Founded by Warren, eHarmony has grown to more than than 33 million registered users in 191 countries, according to its web site.

The management change will likely delay a long-anticipated initial public offering. On the secondary markets, the company is valued at about $660 million, according to Shares Post Inc., an exchange for shares of private companies. It has raised more than $100 million from private equity investors such as Sequoia Capital and Technology Crossover Ventures.