Peter Yarrow, whose caring and righteous singing made the trio Peter, Paul and Mary one of the most popular folk acts of the 1960s, died Tuesday at his home on Manhattan’s Upper West Side. He was 86.

His death was confirmed by Ken Sunshine, his publicist. Mr Sunshine said the cause was bladder cancer, which Mr Yarrow had been battling for four years.

On many of the trio’s recordings, they split the vocal parts evenly, intertwining Mr. Yarrow’s precise tenor with Noel Paul Stookey’s gentle baritone and Mary Travers’ warm alto. But Mr. Yarrow also had some prominent lead singers and led such well-known group recordings as “Puff the Magic.” Dragon,” “Day Is Done,” and “The Great Mandala,” all of which he either wrote or co-wrote. “Puff” became a No. 2 Billboard hit, while “Day Is Done” reached the Top 20.

Mr. Yarrow wrote many other songs recorded by the group, often in collaboration with Mr. Stookey, the last surviving member of the group (Ms. Travers died in 2009 at age 72).

In their peak years, Peter, Paul and Mary reached the Billboard Top 40 twelve times; Six of those songs made the Top 10, including one, her cover of John Denver’s “Leavin’ on a Jet Plane,” which reached No. 1. They landed five Billboard Top 10 albums and topped the magazine’s album charts twice.

Like many folk groups of the time, Peter, Paul and Mary were known for their progressive politics as well as their music. In August 1963 they participated in the March on Washington, where Rev. Dr. Martin Luther King Jr. gave the “I Have a Dream” speech. At a performance on the steps of the Lincoln Memorial, they sang Bob Dylan’s “Blowin’ in the Wind,” which they made a Top 5 Billboard hit that month; Their performance in Washington helped establish it as a civil rights anthem.

The trio also recorded songs and performed concerts in support of liberal presidential candidates Eugene McCarthy in 1968 and George McGovern in 1972. Mr. Yarrow’s lyrics often emphasized the group’s political commitment: “The Great Mandala,” released in 1967, told the story of a war protester on hunger strike; “Day Is Done” (1969), addressed to his son, suggests that the coming generation could create a more just world.

“Day Is Done” and “Puff the Magic Dragon,” both of which featured simple sing-along choruses and deliberately innocent viewpoints, doubled as children’s songs. Decades later, Mr. Yarrow turned each into an illustrated children’s book. “Puff” also inspired a 1978 animated TV special that was so popular that there were two sequels.

Peter Yarrow was born on May 31, 1938 in Manhattan to Bernard and Vera (Burtakoff) Yarrow, Jewish immigrants from Ukraine. His father, a lawyer, was an assistant district attorney in New York under Thomas E. Dewey. He later became vice president of the CIA-funded organization Radio Free Europe.

Mr Yarrow’s parents divorced when he was five years old. His father later converted to Protestantism, but Mr. Yarrow considered Jewish teachings an important inspiration in his life.

He studied painting at the High School of Music and Art (now Fiorello H. LaGuardia High School of Music & Art and Performing Arts) in Manhattan. While at Cornell, he began singing and playing guitar after taking a course on American folk literature with folklorist and historian Harold William Thompson.

After graduating, Mr. Yarrow moved to New York City and became an artist in the fertile Greenwich Village folk scene. “I had this idea that I wanted to get involved in music that creates community,” he told music magazine Rebeat in 2015 — music, he added, “that reaches people’s hearts and mobilizes people for a more humane society.”

His success in the Village led to an invitation to appear on the CBS television special Folk Sound USA in 1960. This also gave him the chance to perform at the Newport Folk Festival, where he met Albert Grossman, a founder of the festival and the manager of singer Odetta.

Mr. Grossman wanted to form a new group that would expand and update the formula of the Weavers, a folk harmony group consisting of one woman and three men (one of them Pete Seeger) that had great success in the 1950s. He introduced Mr. Yarrow to Ms. Travers, who had performed in village clubs and sung with Mr. Seeger several times. The duo became a trio when, at Ms Travers’ suggestion, they added Noel Paul Stookey, with whom she had performed at a local club. They used Mr. Stookey’s middle name and settled on her catchy Biblical nickname.

The trio presented a compelling visual image: The two men, wearing dark ties, beatnik goatees and serious expressions, flanked Ms. Travers, whose blonde hair framed her refined cheekbones. Mr. Grossman booked her for a run at the Bitter End on Bleecker Street, and there was a big stir. In 1961, the group signed with Warner Bros. Records, where their debut album, simply titled Peter, Paul and Mary, was released the following May.

Mr. Yarrow sang lead on the group’s first single, “Lemon Tree,” based on a Brazilian folk song that reached the Billboard Top 40. The full album rose after their second single, “If I Had a Hammer,” written by Pete Seeger and Lee Hays of the Weavers, became a Top 10 hit and won two Grammy Awards. The album remained in the top 20 for two years and sold more than two million copies.

The group’s follow-up, “Movin’,” released in early 1963, included “Puff the Magic Dragon,” the lyrics of which were based on a poem written by a friend of Mr. Yarrow’s, Lenny Lipton, when he was 19. inspired by an earlier poem by Ogden Nash entitled “The Tale of Custard the Dragon.” Speculation later arose that the song referred to smoking marijuana, an interpretation which Mr. Yarrow strongly denied.

In June 1963, the trio released their cover of “Blowin’ in the Wind.” (Bob Dylan was another of Mr. Grossman’s customers.) An estimated 300,000 copies were sold in the first week. By mid-August it had reached number 2; It sold more than a million copies. Her version of another Dylan song, “Don’t Think Twice, It’s All Right,” made the Billboard Top 10 and propelled the author’s own album, “The Freewheelin’ Bob Dylan,” into the Top 30.

In 1964, Mr. Yarrow joined the board of the Newport Folk Festival. In 1970 he conceived the New Folks Concert at the Kerrville Folk Festival in Texas, which became an annual event. The year before, he had helped organize the National Mobilization to End the War, an anti-Vietnam War protest in Washington that was attended by an estimated half a million people.

Peter, Paul and Mary had the biggest hit of their careers in 1970 when “Leavin’ on a Jet Plane,” featuring Ms. Travers’ wistful alto, reached No. 1. But just a few months later they announced their separation.

They separated partly to pursue solo careers but also because Mr. Yarrow was accused of making sexual advances toward a 14-year-old girl who had come into his dressing room with her 17-year-old sister to ask for an autograph 1969. He served three months of a one- to three-year sentence after pleading guilty to taking “indecent liberties” with the girl.

In 1981, Mr. Yarrow received a presidential pardon from Jimmy Carter, although the case continued to be a campaign issue for politicians Mr. Yarrow supported for many years.

In 2019, at the height of the #MeToo movement against sexual abuse of women, a planned appearance by Mr. Yarrow at an arts festival in upstate New York was canceled in response to protests. A remorseful Mr Yarrow responded in a statement saying the organizers’ decision to exclude him was neither “unfair nor unjust”.

“I am not trying to minimize or excuse what I did, and I cannot adequately express my apology and regret for the pain and hurt I have caused,” he said in a statement to the New York Times.

In 1969, Mr. Yarrow married Marybeth McCarthy, a niece of Democratic presidential candidate Eugene McCarthy. (Mr. Stookey wrote “Wedding Song,” which has since been performed in their honor at wedding ceremonies around the world.) The marriage ended in divorce, but they married again in 2022. In addition to her, Mr. Yarrow is survived by a son, Christopher; a daughter, Bethany; and a granddaughter.

Mr. Yarrow released his first solo album, “Peter,” in 1972, but sales were slow. He had far greater success four years later with “Torn Between Two Lovers,” a song he co-wrote with Phillip Jarrell that became a No. 1 hit for mediocre pop singer Mary MacGregor.

Peter, Paul and Mary met for one-off benefit concerts in 1972 and 1978. After their second reunion, they began touring regularly, performing until Ms. Travers’ death. Since then, Mr. Yarrow and Mr. Stookey have appeared together regularly.

In a statement on Tuesday, Mr. Stookey called Mr. Yarrow his “creative, irrepressible, spontaneous and musical younger brother,” but added that he also “became grateful for and loved wisdom mature beyond his years.” and inspiring leadership that he shared with me like an older brother.”

“Perhaps Peter was one of the two brothers I never had,” Mr. Stookey said, “and I will miss both of them deeply.”

In 2000, Mr. Yarrow helped found Operation Respect, a nonprofit organization dedicated to combating bullying and promoting tolerance among children.

Later he often performed with his daughter and the cellist Rufus Cappadocia in a trio called Peter, Bethany and Rufus. Their success strengthened Mr. Yarrow’s confidence in his chosen genre.

“I believe that folk music has had a positive impact on the decency, humanity and empathy of society,” he told Reuters in 2008. “Peter, Paul and Mary had a huge audience, some of whom disagreed with our politics. But they were touched by the human essence of our songs.”

Ash Wu contributed to reporting.