Advertising company Interpublic Group said it would sell about half of its stake in Facebook for $133 million.
Interpublic did not reveal the number of shares it would sell, but said it will record a pre-tax gain of $132 million on the sale.
Facebook, which is mulling a public listing, has roughly 2.4 billion outstanding shares, according to data from secondary market company Sharepost.
In April, The Financial Times had reported that Interpublic owned a 0.4 percent stake in the world's No 1 social networking site. Based on that, Monday's deal would value Facebook at $65.50 billion.
"The Strategic value of our initial investment (in Facebook) has moderated, while the financial value of that stake appreciated significantly," Chief Executive Michael Roth said in a statement.
In June, investment fund GSV Capital Corp bought 225,000 shares in Facebook at an average price of $29.28 each, valuing the world's No 1 social networking site at about $70 billion.
Interpublic also said it plans to increase its share repurchase plan by $150 million to $450 million. It had purchased repurchased about $187.6 million of shares till August 12.
Shares of the company closed at $8.46 on Friday on the New York Stock Exchange.