By Liz Hoffman

Roger Altman founded Evercore Inc. in 1995 after a long career on Wall Street and Washington. He's now laying the groundwork to make sure it thrives after he exits.

Evercore will elevate a pair of executives, Ralph Schlosstein and John S. Weinberg, to be co-chief executive officers and co-chairmen of the board, allowing the 74-year-old Mr. Altman, Evercore's senior chairman, to take another step back from the firm he built into a small but notable player on Wall Street.

The moves essentially mutualize what had been split responsibilities; Mr. Schlosstein had previously been the firm's sole CEO, while the younger Mr. Weinberg, recruited from Goldman Sachs Group Inc. four years ago, had tended to the board alone.

"We found we were operating as equal partners for two to three years, and this formalizes that," Mr. Schlosstein, who is 69, said in an interview.

Wall Street's boutiques--smaller firms, many founded and bulked up during the talent exodus that followed the 2008 financial crisis--are growing up. These firms specialize in corporate advice, rather than lending or securities trading, and pitch themselves as consiglieres rather than financial superstores. Evercore is one of the oldest and by far the biggest, with 1,900 people and $2 billion in annual revenue, most of it from advising on mergers and corporate bankruptcies.

Mr. Schlosstein bristles a bit at the boutique label, saying it "speaks to a scale we've outgrown." Evercore was No. 4 last year on Wall Street in advisory revenue, trailing only Goldman, Morgan Stanley and JPMorgan Chase & Co.--all global firms with dozens of business lines.

Mr. Schlosstein joined Evercore as CEO in 2009, when Mr. Altman took his first steps back. A co-founder of BlackRock Inc., he was seen as strongest in asset management, where Evercore maintains a small business but has scaled back broader ambitions.

Mr. Weinberg, 63, belongs to one of the last Wall Street dynasties. His grandfather, Sidney Weinberg, and later his father, John L. Weinberg, ran Goldman for much of the 20th century. A cousin, Peter Weinberg, is a founding partner and CEO of Perella Weinberg, a rival boutique.

Mr. Altman started his career at Lehman Brothers and joined a young Blackstone Inc. in the late 1980s. He served in two White Houses, first in the Carter administration, where he helped save Chrysler from bankruptcy, and later as Bill Clinton's deputy Treasury secretary. He was seen as a fast riser in the party but left the White House in 1994 after bruising testimony during the Whitewater investigation.

He launched Evercore a year later and has remained a player in Democratic politics, advising Hillary Clinton on her 2008 presidential bid and appearing on the shortlist to be Barack Obama's chief economic counselor. He is seen as someone to whom former Vice President Joe Biden might turn on economic issues should he win in November.

Now Mr. Altman, who remains close to several key firm clients, is taking steps to institutionalize Evercore. Other boutiques, such as Greenhill & Co., have struggled after their founders faded, relied too heavily on poaching from big banks, or struggled to break out of industry niches.

Mr. Weinberg said 40% of Evercore's partners are homegrown. "What really struck me when I joined was this extraordinarily talented generation of bankers in their 40s, coming up," he said.

The new co-CEOs face a likely contraction in mergers as corporate clients wait out the uncertainty of a recession from the coronavirus. They said Evercore's restructuring business, plus a smaller business advising companies on how and where to raise money, would help compensate.

Mr. Schlosstein added that there is "plenty of white space" to chase clients in new sectors and take on rivals such as Lazard Ltd. and Rothschild & Co. on their home turf in Europe.

Write to Liz Hoffman at liz.hoffman@wsj.com