The owner of Dunkin' and Jimmy John's is acquiring Subway in a major deal that could turbocharge the giant sandwich chain's growth globally after its brick-and-mortar footprint shrank in recent years.

Atlanta-based private equity firm Roark Capital emerged as the winning bidder for Subway, a family-owned company for nearly 60 years with headquarters in Milton, Connecticut, and Miami. Subway, a quick-service chain with restaurants owned and run by franchisees, has nearly 37,000 locations in more than 100 countries, making it the second-largest restaurant chain internationally, behind No. 1 McDonald's, which has 40,275 sites.

In a statement Thursday, Subway said it had entered into a definitive agreement to be acquired by Roark in a deal that would combine "Subway's global presence and brand strength with Roark's deep expertise in restaurant and franchise businesses." With the help of its new owner, analysts said, Subway has the potential to gain traction against McDonald's and other rivals by debuting thousands of new locations.

Terms of the sale weren't disclosed, but The Wall Street Journal previously reported that Roark had bid $9.6 billion, which would make it one of the biggest dining-related deals ever. Subway declined to comment on the sales agreement, and Roark didn't immediately return emails from CoStar News seeking a comment.

The pending deal is the latest — and the priciest — in a series of U.S. restaurant mergers and acquisitions this year as Americans resume eating out in the wake of the pandemic.

Earlier this month Bain Capital Private Equity said it was buying Fogo de Chão, the chain of Brazilian-style steakhouses, for a reported $1.1 billion. Fiesta Restaurant Group, parent of the Pollo Tropical chain, recently announced it was being bought for $225 million by Authentic Restaurant Brands. And Darden Restaurants, the parent of live Garden, acquired Ruth's Chris Steak House for $712 million in June.

In 1965 Fred DeLuca and Peter Buck opened the shop, Pete's Super Submarines, in Connecticut that expanded into an international sandwich powerhouse. At its peak in 2015, Subway had about 27,000 U.S. locations, but it has since closed thousands, ending up with 20,576 last year, according to Technomic. Subway faced operational issues, problems with franchises and competition from a host of new sandwich-selling rivals, like fast-growing Jersey Mike's Subs.

In response, Subway took action such as hiring a CEO from outside the company, ex-Burger King CEO John Chidsey; shuttering money-losing locations; updating its menu; doing a lot of promotion; and focusing on international growth. Since 2021, Subway has signed 15 master franchise agreements for more than 9,000 future restaurants worldwide.

Roark has $37 billion in assets under management. Its Inspire Brands owns Dunkin', Arby's, Sonic, Buffalo Wild Wings and Jimmy John's. And another Roark holding company, Focus Brands, owns Carvel, Auntie Anne's, Cinnabon, Moe's Southwest Grill, Schlotzsky's and Jamba.

"This transaction reflects Subway's long-term growth potential, and the substantial value of our brand and our franchisees around the world," Chidsey said in a statement.

He didn't comment to CoStar News, but he told the Journal that Subway, backed by Roark, aims to open about 23,000 new restaurants internationally in the next few years, which would take its store count to 60,000.

"Roark Capital’s purchase of Subway — in what appears to be the third largest food-service deal — is a sizable bet on a chain that, while very well known, has sometimes struggled to generate growth," Neil Saunders, managing director of GlobalData, said in a note on Thursday. "However, given Roark’s extensive experience and investments in the food-service sector and its record of nurturing restaurant brands and helping them to grow, it clearly sees an opportunity to apply the same playbook to Subway. Roark’s strong operating experience will also be helpful to Subway, especially in the U.S. market where it remains well below the peak it hit a few years ago."

The two bigger food-service deals were Burger King's $11.4 billion acquisition of Tim Hortons and Inspire Brands' purchase of Dunkin' for $11.3 billion, according to Saunders.

"As Mr. Saunders notes, Roark has a long, proven history in the restaurant industry and understands the franchise model with a strong leadership team, results-driven culture and shared commitment to transformation," a Subway spokesman said in an email to CoStar News. " We look forward to leveraging Roark’s expertise in the industry as we continue to focus on delivering a consistent, high-quality guest experience, boosting profitability for our franchisees and enhancing our position as a leading restaurant brand."

Technomic ranks Subway as the biggest sub-style sandwich chain in the United States, and the No. 8 fast-food chain for racking up $9.8 billion in domestic sales last year.

Subway's owners, the DeLuca and Buck families, put the chain up for sale in February, and were looking for $10 billion, according to several media reports. In addition to Roark, the bidders reportedly included TDR Capital and Sycamore Partners. Earlier this week, Reuters reported that Roark had set conditions on its bid to buy Subway, such as such as deferring payment on part of the deal consideration, and meeting certain milestones for Subway’s cash flow for the full price to be paid after the deal closes.

Subway has seen its 10th consecutive quarter of positive same-store sales, according to the company. But foot traffic has slipped at U.S. Subway restaurants. In July it was basically flat, up less than 1%, compared with July last year, according to Placer.ai. It dropped 18.5% compared with July 2019.

JP Morgan Chase is serving as financial adviser, and Sullivan & Cromwell is serving as legal counsel to Subway.