"FarmVille" game maker Zynga Inc said Chief Financial Officer David Lee was stepping down and Chief Accounting Officer Michelle Quejado was taking over as interim CFO.
Zynga also said it would delay the launch of the "Dawn of Titans" and "CSR2" games to 2016 from the fourth quarter planned earlier.
The company has struggled to adapt to gamers shifting to mobile devices and fierce competition from newer rivals such as King Digital Entertainment Plc and Glu Mobile Inc .
"Developing new sustainable growth continues to be challenging and unpredictable," Zynga said in a letter to shareholders on Tuesday.
Founder Mark Pincus, who returned as chief executive this year, has been focusing on cutting costs and reducing Zynga's slate of games.
The delay in the launch of the two games brings down the number of launches this year to five, with "Princess Bride Slots" expected to be released in the current quarter.
The company had earlier said it planned to launch six-eight mobile games in 2015.
Zynga reported bookings of US$176 million (S$246 million) for the third quarter, beating the average analyst estimate of US$170.8 million, according to research firm FactSet StreetAccount.
However, the company forecast bookings of US$165 million-US$180 million for the current quarter, well below analysts'expectations of US$193.9 million.
Bookings equal revenue recognized in a period plus the change in deferred revenue. Zynga records the sale of virtual goods and downloads as deferred revenue, which is added to the company's books as and when these items are consumed.
Videogame maker Activision Blizzard Inc said earlier on Tuesday that it would buy King Digital for US$5.9 billion to expand its mobile games push.
Zynga's revenue rose 10.8 percent to US$195.7 million in the quarter ended Sept. 30, helped by the success of games such as"Wizard of Oz Slots" and "Words With Friends".
It posted a profit of US$3.1 million, or breakeven per share, compared with a year-earlier loss. Zynga also said it would buy back up to US$200 million in shares.
Lee, who joined the company from Best Buy Co Inc in April last year, will leave the gaming company in December.
Zynga's shares were up slightly at US$2.48 in extended trading on Tuesday, after closing 2.5 percent higher after news of the Activision deal.