Mayor Bill de Blasio has reached a deal with the Sergeants Benevolent Association, leaving just one NYPD union without a contract and finding “common ground” with a union whose leader had been one of the most strident critics of City Hall’s policing policies.

“With this contract agreement, we have four contract agreements with our NYPD unions, three of which as you know have been ratified,” Mr. de Blasio said.

The SBA, led by one-time de Blasio critic Edward Mullins, had been the only union representing superior uniformed officers that did not have a contract with the city, after eight unions representing higher-ups at the NYPD, Correction, Sanitation and Fire Departments joined together in a coalition and signed a deal in December.

Today’s agreement is largely the same as those unions agreed to. Like the previous deal, it includes the health care savings established by the United Federation of Teachers deal, but departs from that pattern by including an extra 1 percent raise in the first year of the contract. Mr. de Blasio had said it is a show of understanding the unique risks the uniformed city workers take.

The SBA deal does have some slight differences from the coalition’s deal. The retroactive raises start earlier, in the first month of the first year of the contract rather than the last month. There are also some longevity payments paid for by other benefit changes, City Hall director of labor relations Robert Linn said.

The city still has not reached a contract with the Patrolmen’s Benevolent Association, which is by far the largest police union, representing the city’s rank-and-file cops. The PBA’s leader, Patrick Lynch, has also been a critic of the mayor, saying City Hall had “blood” on its hands after two police officers were murdered in December.

The PBA is in binding arbitration over its contract after reaching an impasse with the city. Mr. Lynch has taken his contract negotiations to arbitration several times before, seeking to get a better deal than the city has offered.

“We’ve been saying to the PBA all along, we’re ready to sit down we’re ready to find solutions to our problems and we should do that,” Mr. Linn said, but he said that has not been happening yet. “No discussions going on. We’re working on dates for the arbitration.”

The rest of the city’s rank-and-file uniform unions have also have not signed contracts—likely awaiting the PBA’s deal and hoping to receive something comparable.

It was perhaps not surprising that the SBA had been a hold-out in the earlier superior officer coalition deal. Mr. Mullins had been a fierce critic of the mayor—he once called him a “nincompoop.” He urged the Democratic National Convention not to come to Brooklyn, saying it was too unsafe. He slammed the mayor for employing as his wife’s chief of staff Rachel Noerdlinger, whose boyfriend had a criminal record and had used anti-cop rhetoric.

But in recent months, following a sit-down meeting, Mr. Mullins’ tone had softened.

“The fact that we together found common ground, I think sends a very positive message about what can be achieved when people seek common ground. Our door is always open at City Hall,” Mr. de Blasio said.

Asked what’s changed, Mr. Mullins said there had been a “re-focus” on what was important: the people of the city.

“The City of New York, which I believe is the capital of the world, should not crumble, and it shouldn’t crumble because of two people stomping their feet on the ground,” Mr. Mullins said.