The owner of agencies including McCann Erickson, Lowe and Draftfcb paid $5m (£3.09m) for less than 1% in Facebook in 2006, according to a report by The Financial Times.
Investments in Facebook have rarely been from the ad sector, but reports suggest IPG also guaranteed a $10m (£6.19m) spend by clients to help kick-start interest in Facebook’s ad platform.
The exact value of the stake isn’t known but it’s estimated to now be worth between $200m and $300m.
When IPG made its investment in 2006, the social network was worth $1bn. Following investment of $1bn by Goldman Sachs in January, it was valued at over $50bn.