Cliff Joseph, an artist raised in Harlem who in the 1960s and ’70s led protests against major New York museums to advocate for the inclusion of Black artists, and who later pioneered the practice of multiculturalism in the field of art therapy, died on Nov. 8 in a hospital in Chicago. He was 98.

His wife, Ann Joseph, confirmed the death.

In 1963, Mr. Joseph, whose paintings depicted the social unrest sweeping the nation, was struggling as an artist in New York. He was in Washington that August, standing at the front of the crowd at the Lincoln Memorial when the Rev. Dr. Martin Luther King Jr. delivered his “I Have a Dream” speech.

“I was so moved by that experience and what it said to me about the way I should be using my art skills,” Mr. Joseph said in a 2006 documentary, “Conversations With Cliff Joseph.” “This really awakened me.”

Mr. Joseph and a group of other artists founded the Black Emergency Cultural Coalition, which began agitating for the inclusion of African-American artists in New York museums.

When the Metropolitan Museum of Art opened the show “Harlem on My Mind” in 1969, their cause gained attention. The exhibition, which documented the culture and history of Harlem, included no paintings or sculptures by Black artists. Mr. Joseph and his fellow activists picketed outside the museum for days with signs that read, “Harlem on Whose Mind?”

Their voices were heard.

Mayor John V. Lindsay criticized the exhibition. The New York State Division of Human Rights denounced it. And the Met’s curator, Thomas Hoving, issued a rare public apology.

In 1971, the Whitney Museum of American Art opened an exhibition called “Contemporary Black Artists in America.” The coalition criticized the museum for assigning a white curator to the project.

“It is essential,” Mr. Joseph said in a statement, “that it be selected by one whose wisdom, strength and depth of sensitivity regarding Black art is drawn from the well of his own Black experience.”

The Whitney’s director, John I.H. Baur, told the news media, “The coalition stands for a kind of separatism I don’t believe in.”

Fifteen Black artists, including the sculptor Richard Hunt and the painter Sam Gilliam, withdrew from the exhibition on its opening day. Soon after that, the group staged a protest show, “Rebuttal to Whitney Museum Exhibition,” at Acts of Art, a Black-owned gallery in Greenwich Village.

After the inmate uprising at the Attica Correctional Facility in upstate New York in 1971, the group lobbied for the implementation of arts programs for prisoners, and Mr. Joseph sent a letter to Gov. Nelson A. Rockefeller.

“Those who are at the head of the oppressive system know well the power of art and fear it in the hands of the people,” he wrote. “That is why power structures throughout man’s history have sought to suppress and control the creative artist.”

That same year, their arts program, often taught by artists from the coalition, was implemented at the Tombs in Lower Manhattan, later expanding to correctional facilities across the country.

In his 40s, Mr. Joseph entered the mental health field of art therapy, helping to introduce concepts like racial sensitivity and cultural competency to the profession.

He taught art therapy at Pratt Institute in Brooklyn for 11 years and worked at Albert Einstein College of Medicine in the Bronx. He was the first Black member of the American Art Therapy Association and became president of the New York Art Therapy Association in 1981.

In the 2006 documentary, Mr. Joseph reflected on his contributions to multiculturalism in his field.

“It’s not that a person has to be Black to deal with Black patients,” he said. “But if a white person comes in to deal with a group of Black people, that person should know that a culture-specific approach should be used.”

Otherwise, he continued, “they’re not going to understand where you’re coming from, and you won’t understand where they’re coming from, and nothing is going to happen.”

Clifford Ricardo Joseph was born on June 23, 1922, in Panama City to a large Caribbean family. His father, Samuel, worked on the construction of the Panama Canal, and his mother, Leontine (Ellis) Joseph, was a maid. When he was 18 months old, his family settled in Harlem.

Cliff’s older brother, Freddy, aspired to become a police officer; the same day he was admitted into the academy, he was fatally shot by a man in his apartment building. To support his family, Mr. Joseph enlisted in the Army as a teenager. He later served overseas in a field artillery unit.

After World War II, Mr. Joseph studied at Pratt on the G.I. Bill, graduating with a B.F.A. in 1952. While working at a welfare center, he met Ann Voggenthaler, whom he married in the mid-1960s.

A few years after attending the March on Washington with his wife and hearing Dr. King speak, Mr. Joseph mailed Dr. King some Christmas cards he had designed honoring the young girls killed in the Ku Klux Klan bombing of a church in Birmingham, Ala., in 1963. Dr. King sent a letter to Mr. Joseph’s East Village apartment.

“I was deeply impressed and very grateful for your generous gesture,” he wrote. “It was especially gratifying since I have always felt, since I first saw it, that your art expressed the meaning and sacrifice of our struggle.”

In the 1960s, Mr. Joseph helped take care of psychiatric patients at Jacobi Hospital in the Bronx, where he befriended Edith Kramer, a prominent art therapist. Ms. Kramer invited him to watch her work with children at the hospital, and Mr. Joseph was moved by what he witnessed. She then brought him to the early meetings of the American Art Therapy Association.

“I got into this room with all these people and I didn’t see anyone that I could recognize as being of my race,” Mr. Joseph said in 2006. “I felt there was some politeness when I was introduced, but I didn’t feel I was being welcomed in.”

The American Art Therapy Association gave Mr. Joseph an award in 2008 acknowledging his commitment to social activism in the field. He was also featured in a documentary, “Wheels of Diversity in Art Therapy: Pioneers of Color,” which profiled several therapists who introduced a multicultural perspective.

In 2001, after years living in the rent-regulated Westbeth Artists Housing complex in the West Village, Mr. Joseph and his wife moved to Chicago, where they later joined the neighborhood protest of a petroleum coke storage facility on the Southeast Side owned by the Koch brothers. Mr. Joseph also wrote a science-fiction novel, “The Revelation of Number 10: A Galactic Neighbor’s Appeal.”

In addition to his wife, Mr. Joseph is survived by two children from a previous marriage, Clifford Jr. and Leonette Joseph; a brother, Ronald; and three grandchildren. A daughter, Zuri Joseph, died in 2013.

In 2018, Hunter College in New York revisited “Rebuttal to Whitney Museum Exhibition” with an event at its campus gallery. The exhibition remounted works from the original 1971 show, including one of Mr. Joseph’s oil paintings, “The Superman.”

That painting depicts a bloated Klansman holding a rifle and a cross standing in front of a Confederate flag. But he is naked, carrying his white robe on his arm, and Mr. Joseph has rendered him spectral and forlorn.