NORRISTOWN, Pa. — A jury found Bill Cosby guilty Thursday of drugging and sexually assaulting a woman at his home near here 14 years ago, capping the downfall of one of the world’s best-known entertainers, and offering a measure of satisfaction to the dozens of women who for years have accused him of similar assaults against them.

On the second day of its deliberations at the Montgomery County Courthouse, the jury convicted Mr. Cosby of three counts of aggravated indecent assault against Andrea Constand, at the time a Temple University employee.

Mr. Cosby’s case was the first high-profile sexual assault trial to unfold in the aftermath of the #MeToo movement and many considered the verdict a watershed moment, one that reflected that, going forward, the accounts of female accusers may be afforded greater weight and credibility by jurors.

The Montgomery County district attorney, Kevin R. Steele, asked that Mr. Cosby’s $1 million bail be revoked, suggesting he had been convicted of a serious crime, owned a plane and could flee, prompting an angry outburst from Mr. Cosby, who shouted, “He doesn’t have a plane, you asshole.”

“Enough of that,” Judge Steven T. O’Neill said. He did not view Mr. Cosby as a flight risk, he said, adding that he could be released on bail but that he would have to remain in his nearby home. The judge did not set a date to sentence Mr. Cosby on the three counts, all felonies and each punishable by up to 10 years in state prison.

The National Organization for Women called the verdict a “notice to sexual predators everywhere.” Rose McGowan, one of the women who has accused Harvey Weinstein of assault, tweeted a thank you to the judge and jury and to “society for waking up.” Gloria Allred, the lawyer who represented many of Mr. Cosby’s accusers, hailed the decision as an important breakthrough.

“After all is said and done, women were finally believed,” she said outside the courtroom.

The impression of change was evident within the trial itself when the defense attacked the credibility of five women who had testified that they, too, believed Mr. Cosby had drugged and sexually assaulted them. Kathleen Bliss, one of Mr. Cosby’s lawyers, called one of the women a failed starlet who slept around. She branded another a publicity seeker.

The remarks inflamed Kristen Gibbons Feden, a prosecutor on the case. She called the attacks filthy and shameful and the sort of criticism that had long kept sexual assault victims from coming forward. Ms. Feden’s colleague, M. Stewart Ryan, described Ms. Bliss’s approach as “the last vestiges of a tactic not to get to the truth, but to damage character and reputation.”

Their boss, Kevin R. Steele, the Montgomery County district attorney, referenced the broader significance of the case when he thanked Ms. Constand for taking part in not one, but two trials. “She has been a major factor in a movement that has gone in the right direction, finally,” he said.

The first trial ended with a hung jury after six days of deliberations last summer. When the jury announced its decision Thursday, Mr. Cosby sat back in his chair and quietly stared down. Several women who have accused him of abuse, and attended the trial each day, briefly cheered. Ms. Constand, who had been quiet throughout, stood up and was hugged by supporters, including her lawyer.

Mr. Cosby did not comment as he left the courthouse, but his lead lawyer, Thomas A. Mesereau Jr., said his client would appeal. “We are very disappointed by the verdict,” he said. “We don’t believe Mr. Cosby is guilty of anything.”

In recent years, Mr. Cosby, 80, had admitted to decades of philandering, and to giving quaaludes to women as part of an effort to have sex, smashing the image he had built as a moralizing public figure and the upstanding paterfamilias in the wildly popular 1980s and ’90s sitcom “The Cosby Show.” He did not testify in his own defense, avoiding a grilling about those admissions, but he and his lawyers have insisted that his encounter with Ms. Constand was part of a consensual affair, not an assault.

The verdict now marks the bottom of a fall as precipitous as any in show business history and leaves in limbo a large slice of American popular culture from Mr. Cosby’s six-decade career as a comedian and actor. For the last few years, his TV shows, films and recorded stand-up performances, once broadcast staples, have largely been shunned, and with his conviction, they are likely to remain so.

At Mr. Cosby’s retrial, in the same courthouse and before the same judge, a new defense team argued unsuccessfully that Ms. Constand, now 45, was a desperate “con artist” with financial problems who steadily worked her famous but lonely mark for a lucrative payday.

The prosecution countered that it was Mr. Cosby who had been a deceiver, hiding behind his amiable image as America’s Dad to prey on women that he first incapacitated with intoxicants. During closing arguments Tuesday, Ms. Feden told the jury: “She is not the con. He is.”

The defense’s star witness was a veteran academic adviser at Temple who said Ms. Constand had confided to her in 2004 that she could make money by falsely claiming she had been molested by a prominent person. Mr. Cosby paid Ms. Constand $3.38 million in 2006 as part of the confidential financial settlement of a lawsuit she had brought against him after prosecutors originally declined to bring charges.

But Ms. Constand said she had never spoken with the adviser, and prosecutors rebutted her characterization as a schemer. Perhaps most damaging to Mr. Cosby, was the testimony from five other women who told jurors they, too, were Cosby victims. The powerful drumbeat of accounts allowed prosecutors to argue that Ms. Constand’s assault was part of a signature pattern of predatory behavior.

Mr. Cosby’s lawyers had tried to block the additional women from testifying, arguing their accounts would be prejudicial. They noted that the scrutiny of sexual assault had heightened, and recently had ensnared a group of high-profile men, but they said it was only Mr. Cosby who was on trial in this instance. “Mob rule is not due process,” Ms. Bliss told the jury.

When Ms. Constand testified, she took the stand as something of a proxy for the other women, more than 50, who have accused Mr. Cosby of abuses.

None of those accusations had resulted in prosecution. In many of the cases, too much time had passed for criminal charges to be considered, so Ms. Constand’s case emerged as the only criminal test of Mr. Cosby’s guilt.

But Mr. Cosby has been sued by several accusers, some of whom said he or his staff defamed them by dismissing their allegations as fabrications.

The suits are likely to draw momentum from the guilty verdict.

Many of the accusers celebrated the verdict with laughter and tears. Patricia Steuer, 61, who accused Mr. Cosby of drugging and assaulting her in 1978 and 1980, said she and her husband were in a pharmacy at Lake Tahoe when the news arrived by text.

“We just collapsed in each other’s arms,” she said. “We were just crying.”

The case largely turned on the credibility of Ms. Constand, who testified that during a visit in early 2004 to Mr. Cosby’s home near Philadelphia, when she was 30 and he was 66, Mr. Cosby gave her pills that left her immobile and drifting in and out of consciousness. He said he had only given her Benadryl.

In Mr. Cosby’s first trial, only one other accuser had been allowed to testify. At the retrial, the five additional witnesses included the former model Janice Dickinson, who told jurors Mr. Cosby had assaulted her in a Lake Tahoe hotel room in 1982, after giving her a pill to help with menstrual cramps. “Here was America’s Dad on top of me,” she told the courtroom, “a happily married man with five children, on top of me.”

The defense suggested that Ms. Dickinson had made up the account, pointing to her memoir, which recounted the meeting without mentioning any assault. But Ms. Dickinson’s publisher testified that she had shared her account of rape and that it was kept out of the book for legal reasons.

Another accuser, Chelan Lasha, said Mr. Cosby invited her to his suite at the Las Vegas Hilton in 1986, when she was 17, to help her with her modeling career. Mr. Cosby, she said, gave her a pill and liquor, and then assaulted her.

In court, Ms. Lasha, who was often in tears, called across the courtroom to the entertainer.

“You remember,” she asked, “don’t you, Mr. Cosby?”

The defense team tried to convince the jurors that Mr. Cosby’s main accuser, Ms. Constand, saw him as her escape from financial straits. “You are going to be asking yourself during this trial, ‘What does she want from Bill Cosby?’ And you already know the answer: ‘Money, money and lots more money,’” Mr. Mesereau told the jurors as he opened his defense of Mr. Cosby.

The defense emphasized inconsistencies in the version of events Ms. Constand had given the police, saying, for example, at one point that the assault had taken place in March 2004, then later changing that to January 2004.

Mr. Cosby’s lawyers cited her phone records to show she had stayed in touch with him after the encounter and they produced detailed travel itineraries and flight schedules in an effort to show that Mr. Cosby had not stayed at his Philadelphia home during the period in which she said the assault occurred.

“He was lonely and troubled and he made a terrible mistake confiding in her what was going on in his life,” Mr. Mesereau said.

Under cross-examination, Ms. Constand explained the lapses in her accounts as innocent mistakes, and said her contacts with Mr. Cosby after the incident were mostly cursory, the unavoidable result of her job duties.

Mr. Steele told the jury that Mr. Cosby took away Ms. Constand’s ability to consent with the pills he gave her, and that their later contacts were irrelevant.

When Ms. Constand’s mother called to confront Mr. Cosby about a year after the incident, the prosecution argued, his apology and his offer to pay for her schooling, therapy and a trip to Florida were evidence he knew he had done something wrong.

Mr. Steele, the district attorney, also worked to rebut the defense claims. He said that Mr. Cosby, a member of Temple University’s board of directors at the time and the university’s most famous alumnus, set his sights on Ms. Constand, an employee in the athletic department who considered him a mentor.

“This case is about trust,” Mr. Steele had told the jurors. “This case is about betrayal, and that betrayal leading to a sexual assault of a woman named Andrea Constand.”