The restaurateur requested protection under Chapter 11 while it reorganises its finances, according to a filing in US bankruptcy court in New York.
The restructuring will affect about USD 140 million in Sbarro debt, according to report by rating agency Fitch.
Fitch also discussed a possible bankruptcy at Quizno's, another medium-sized restaurant chain.
The Sbarro and Quizno's troubles are "a warning sign of financial distress" confronting many brands in the restaurant industry, Fitch said.
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Both chains have suffered the growth of competitors like Subway, Little Caesars and Papa John's. In Sbarro's case, Fitch said the 68-year-old chain has also lost out from consumers moving away from shopping malls.
Sbarro last month said it was cutting 155 restaurants in North America to reduce costs.
Sbarro's 2011 bankruptcy resulted in an agreement with creditors to trim its debt from USD 368 million to USD 130 million.