Shares in King Digital, the games developer behind Candy Crush Saga, have fallen as much as 15% on their debut at the New York Stock Exchange.
The shares were trading at $19.08 each, down from the listing price of $22.50.
King's flagship game Candy Crush was the most downloaded free app of 2013 and has boosted the firm's revenue.
But there have been concerns it relies too heavily on the game and doubts over whether it will be able to sustain its popularity and growth over time.
The firm's portfolio includes more than 180 games, but only a few have been popular with users.
Its top three games - Candy Crush Saga, Pet Rescue Saga and Farm Heroes Saga - accounted for 95% of its total revenue in the fourth quarter of 2013.
"With King Digital, there is a lot of concern about its ability to keep coming up with popular games," said Jay Ritter, a professor and initial public offering expert at the University of Florida.
The firm had raised $500m (£300m) after it priced its shares at the mid-point of the range it had initially indicated, valuing the company at more than $7bn.
"The offer price was set at the middle of the filed price range, indicating that there was neither exceptionally strong nor exceptionally weak demand," Mr Ritter said.