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 as it prepares to expand globally.
The company works with local businesses to offer steep discounts on services and products such as beauty treatments and meals, if enough users pledge to buy them.
In the UK Groupon was this week after it posted a misleading restaurant deal ad, which "exaggerated" the available discount.
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