Maveron LLC, a venture capital firm that Schultz co-founded, has also made an investment in the company.
Schultz, who is chairman, president and chief executive officer of Starbucks Coffee Company, served as Starbucks CEO from 1987 to 2000, taking the reins again in 2008.
He relinquished his role as CEO to concentrate on global strategy but returned to his job three years ago, replacing CEO Jim Donald, after the coffee chain had been underperforming.
In January, Groupon announced it had completed a US$950 million round of financing as it prepares to expand globally.
The company made headlines across the world last week followings its controversial Superbowl ad referring to the ongoing political repression in Tibet to promote its site.
This article was first published on marketingmagazine.co.uk.