The singer Justin Timberlake pleaded guilty on Friday to driving while impaired, resolving a case that began with his June arrest on drunken-driving charges in the Hamptons.

As part of his plea, Mr. Timberlake agreed to pay a $500 fine and serve 25 hours of community service for a charity of his choosing. He also agreed to a 90-day suspension of his driver’s license in New York.

The singer, who was originally charged with the more serious crime of driving while intoxicated, entered the plea during an appearance at a 30-seat courthouse in the village of Sag Harbor. He wore a black cardigan and khaki slacks, with a double strand of pearls peeking out from beneath a dark T-shirt.

During the hearing, Mr. Timberlake looked on with his hands folded in front of him. His original plea agreement stipulated that he would make a public safety announcement discouraging drinking and driving. Justice Carl Irace, the village court judge overseeing the case, said on Friday that it would be more meaningful for the singer to commit himself to “a period of reflection and contemplation” through community service.

Mr. Timberlake agreed, and acknowledged that he had erred in driving rather than calling a taxi or getting a ride from a friend.

“It was a clear misjudgment,” he said.

Justice Irace, satisfied with Mr. Timberlake’s contrition, commended him for his sincerity. The judge also asked about drug and alcohol counseling for the singer, calling its absence from the plea deal “concerning,” but did not impose it.

Speaking in front of a throng of reporters and cameras outside Sag Harbor Police Headquarters after the hearing, Mr. Timberlake urged people following the case to learn from his mistake.

“Many of you have probably been covering me for a lot of my life, and as you may know, I try to hold myself to a very high standard, for myself, and this was not that,” he said.

The arrest occurred in the early hours of June 18, when a Sag Harbor police officer pulled over a new-model BMW that was driving erratically.

Mr. Timberlake, glassy-eyed and smelling of alcohol, was at the wheel, according to an arrest report. After stepping out of the car, he struggled to complete several sobriety tests, the report said. He was placed in custody and held overnight.

The singer told the police that he was on his way home after having had “one martini.” His lawyer, Edward Burke Jr., insisted to reporters that his client was not drunk when he was arrested. (Mr. Burke’s statements about the charges outside court prompted Justice Irace to scold him at an August hearing.)

The guilty plea concludes a summer of embarrassment for Mr. Timberlake. His arrest inspired a flood of mocking memes and tabloid attention. And even the court dates he did not attend in person drew crowds of reporters and film crews to Sag Harbor’s downtown, where the municipal building is surrounded by clothing boutiques, upscale galleries and the American Hotel. Mr. Timberlake had been seen there imbibing on the night of his arrest.

The legal woes have not interrupted his Forget Tomorrow world tour. He has continued playing stadium concerts, and even cracked a joke about the charges at a show in Boston in June. Justice Irace, acknowledging the demands of Mr. Timberlake’s tour schedule, made the unusual decision to allow the singer to attend the August hearing via video conference from an undisclosed location in Europe.

Mr. Timberlake is scheduled to perform at the Prudential Center in Newark at the end of September as part of a charity show that will benefit a suicide-prevention nonprofit.

Although social media users had a laugh or two at Mr. Timberlake’s expense, some prominent people with ties to the Hamptons sympathized with his public relations headache. In a recent New Yorker profile, the celebrity chef Ina Garten said she felt bad for “poor Justin Timberlake.”

Asked about Mr. Timberlake’s arrest in June, Billy Joel, a Sag Harbor resident who crashed his car three times on Long Island in the early 2000s, advised a local news reporter to “judge not, lest ye be judged.”

On Friday, Sag Harbor’s lesser-known residents were unsympathetic.

Interviewed on Main Street, Helen Hernandez, an accountant with homes in Sag Harbor and Westchester County, said she thought prosecutors should not have agreed to let Mr. Timberlake plead guilty to a less severe charge. Ms. Hernandez said a member of her family had spent $10,000 in legal fees to fight a similar charge in Westchester.

“I’m not a big fan of his,” she said.

Lawrence Rich, a real estate broker who splits his time between Sag Harbor and New York City, said he thought Mr. Timberlake’s celebrity status might have helped his case.

“Rich and famous people get away with things,” he said. “Somebody who’s not rich and famous would be in jail.”