SAN ANTONIO — BDT Capital Partners, L.L.C. has agreed to acquire a majority interest in Whataburger through its affiliated funds. The merchant bank, which specializes in family and founder-led companies, will partner with Whataburger’s leadership team to begin exploring expansion plans.

The transaction is expected to close later this summer and is subject to customary regulatory and other conditions, the company said. Additional terms were not disclosed.

The new partnership isn’t the only change coming to Whataburger. Several tenured leaders within the company have been elevated to the core leadership team as president and chief executive officer Preston Atkinson and board chairman Tom Dobson retire from the company’s day-to-day operations.

“As the brand embarks on a growth and expansion plan, we decided the time was right to promote new leadership to carry the company forward,” Mr. Atkinson said. “This leadership team has the right combination of Whataburger core values, strategic vision and people-centered leadership to take us into the future.”

All positions named to Whataburger’s leadership team were internal promotions and will be effective July 1.

Ed Nelson, currently the company’s chief financial officer and controller, will be promoted to president. Mr. Nelson joined Whataburger in 2004 as controller and has been at the helm of the company’s financial department as c.f.o. since 2008.

Leonard Mazzocco, currently vice-president of business operations, has been elevated to senior vice-president and chief operating officer. Mr. Mazzocco joined Whataburger in 1999 as operations services director before taking on his current role in 2014.

Ron Rodriguez, who joined the company in 2006 as director of operations before being named a senior vice-president in 2014, will assume the role of senior vice-president and chief restaurant operating officer.

 James Turcotte will be promoted to chief development officer while continuing in his current role as senior vice-president of the real estate segment. Mr. Turcotte joined Whataburger in 1999 as a director in the real estate division before taking on the role of group director, followed by vice-president of franchise development. He was named vice-president of property and facilities in 2004.

Current vice-president of retail Mike Sobel will be promoted to senior vice-president of retail. Mr. Sobel joined the company in 2011 as director for supply chain solutions before assuming his current role in 2014.

Michael Gibbs, currently senior vice-president and general counsel, will continue in his role as general counsel and will be promoted to executive vice-president.

Mr. Atkinson and Mr. Dobson will hold seats on the Whataburger board of directors to provide ongoing guidance and ensure a smooth transition. The leadership realignment will allow them to focus on operating the diversified investment company Las Aguilas, which was established by the Dobson family in 2011 and is focused on real estate and philanthropy.

BDT will provide strategic vision and long-term growth capital to Whataburger’s newly realigned leadership team as it begins exploring expansion plans.

“We’re excited about the partnership with BDT because they respect and admire the brand we’ve built,” Mr. Atkinson said. “They want to preserve it while they help us continue growing a sustainable, competitive business over a long period of time. They don’t plan to change our recipe for success.”