attrick was first appointed to the position in July 2013 to drive turn around the company’s fortunes after it was unable to capitalise on the popularity of its ‘Farmville’ title.
Pincus stayed on as chairman and chief product officer, although he relinquished the last of his operational duties last year.
Mattrick focused heavily on Zynga’s mobile gaming efforts during his time as chief executive officer in an attempt to help drive new business.
However, despite these efforts, Zynga has struggled to gain ground in the social gaming market, with its shares having traded below $5 for more than a year.
Shares fell as much as 11% at $2.58 in extended trading following the news of Mattrick’s departure.
Mattrick, who headed up Microsoft Corp’s Xbox business before joining Zynga, will also step down from the company’s board.
In a statement released shortly after his departure was confirmed, Mattrick said he intends to return to Canada in order to pursue his next challenge.
Pincus, who founded the company in 2007, will now return as chief executive officer in an effort to turn around its fortunes.
Speaking in a letetr to Zynga staff, Pincus said: "I am returning to the company that I love in order to accelerate innovation in the most popular categories like Action Strategy and strengthen our focus on our core areas like Invest and Express.
"I look forward to partnering with our leaders to intensify our focus on social experiences for the millions of consumers who play our games.
"Zynga pioneered social gaming for the mass market and our mission to connect the world through games has never wavered.
Zynga was regarded as one of Silicon Valley’s fastest growing companies just a few years ago, but has suffered heavy losses in recent times.
The firm is also facing a lawsuit that accuses it of defrauding shareholders about its prospects both before and after its initial public offering (IPO) in December 2011.