Abraham Johannes Muste was born January 8, 1885, in the small port city of Zierikzee, located in the Southwestern province of Zeeland in the Netherlands. Muste's Father, Martin Muste, was a coachman who drove for a family that was part of Zeeland's hereditary nobility. With his economic prospects limited in the Netherlands, Martin Muste decided to follow four of his wife Adriana's brothers to emigration in America, making the cross-Atlantic trip as Third Class passengers in January 1891.

Along with the rest of his family, A.J. became a naturalized American citizen in 1896. He was just 11 years old at the time of his naturalization.

Following graduation, Muste taught Latin and Greek for the 1905-06 academic year at Northwestern Classical Academy (now Northwestern College) in Orange City, Iowa.

In the fall of 1906, Muste went East to the Theological Seminary of the Dutch Reformed Church, today known as the New Brunswick Theological Seminary, located in New Brunswick, New Jersey. While in New Brunswick, Muste took courses in philosophy at New York University and Columbia University, attending lectures by william James and meeting John Dewey, who became a personal friend. While he remained in training to become a minister of the Reformed Church, retrospectively it seems that Muste began to first question the church's fundamental principles at this time.

He graduated from that institution in June 1909, and was married shortly thereafter to his sweetheart from his Hope College days, Anna Huizenga. Upon his graduation, Muste was appointed pastor of the Ft. Washington Collegiate Church in the Washington Heights neighborhood of Manhattan. During his spare time, Muste availed himself of his parish's proximity to the theologically liberal Union Theological Seminary, taking additional courses there. Muste ultimately received a Bachelor of Divinity degree from Union in 1913, graduating from the institution magna cum laude.

Muste was influenced by the prevalent theology of the social gospel, and began to read the written ideas of various radical thinkers of the day, going so far as to vote for Socialist candidate Eugene V. Debs for President of the United States in 1912. Muste would later claim that he never again voted for a Republican or Democrat for a major national or state office.

Muste remained as pastor of the Fort Washington Collegiate Church on Washington Heights until 1914 when he left the Reformed Church because he no longer ascribed to the Westminster Confession of Faithtthe set of fundamental principles of the denomination.

Thereafter, Muste became an independent Congregationalist minister, accepting a pastorate at the Central Congregational Church of Newtonville, Massachusetts, in February 1915.

A committed pacifist, Muste joined the Fellowship of Reconciliation shortly after its founding in 1916. Muste participated in a peace demonstration late in the summer of 1916, with American entry into the European war looming and some parishioners began to withdraw from Muste's congregation. Pressure began to build further over Muste's pacifist views in April 1917 when the United States formally declared war on the German and Austro-Hungarian Empires. After taking two months of vacation leave during the summer of 1917, Muste decided that the time had come to leave, and in December 1917, he formally resigned his pastorate position.

Later in 1918, Muste moved to Providence, Rhode Island, where he was enrolled as a Quaker minister. Muste received use of a home and money for expenses in exchange for pastoral services. An array of political publications were kept in a large room in the basement of the Providence Meeting House and each Saturday, pacifists, radicals, and an eclectic mix of individuals gathered there to discuss issues of concern.

The workers, many of whom were new immigrants who spoke English poorly or not at all, were without effective leadership through which to express their demands, however. When dissident workers walked off the job in February 1919, only to be met by the use of police truncheons against their pickets, Muste and two other radical ministers with whom he had formed a close friendship became involved. Muste spoke to assembled workers, assured them that he would lend whatever help he could in raising money for the relief of strikers and their families, and was soon invited to become executive secretary of the ad hoc strike committee established by the still unorganized workers. Muste became the spokesman for some 30,000 striking workers, hailing from more than 20 countries. Muste was himself pulled from the picket line as a strike leader, isolated, and clubbed by police, who eventually deposited him in a wagon and hauled him to jail when he could no longer stand. After a week behind bars, the case against Muste for allegedly disturbing the peace was dismissed; the strike continued without interruption, despite the jailing of Muste and more than 100 strikers.

Upon leaving the ATWU, Muste became the first chairman of the faculty at Brookwood Labor College in Katonah, New York, where he remained from 1921 to 1933. During this period Muste cemented his reputation as a recognized leader of the American labor movement.

In 1929 Muste attempted to organize radical unionists opposed to the passive policies of American Federation of Labor President william Green under the banner of an organization called the Conference for Progressive Labor Action (CPLA).

Muste also was a member of the League for Independent Political Action (LIPA), a group of liberals and socialists headed by Philosopher John Dewey which sought the establishment of a new labor-based third party. Muste resigned his position on the LIPA Executive Committee in December 1930 in protest over Dewey's appeal to U.S. Senator George W. Norris of Nebraska to quit the Republican Party to head the third party movement. Muste declared that any such movement must start from the bottom up through the action of organized workers if it was to survive and that it was "of the utmost importance to avoid every appearance of seeking messiahs who are to bring down a third party out of the political heavens."

In 1933, Muste's CPLA took the step of establishing itself as the core of a new political organization called the American Workers Party. This organization was informally referred to as "Musteite" by its contemporaries.

The AWP then merged with the Trotskyist Communist League of America in 1934 to establish a group called the Workers Party of the United States. Through it all Muste continued to work as a labor Activist, leading the victorious Toledo Auto-Lite strike of 1934.

He supported the presidential candidacies of Eugene V. Debs and Robert M. La Follette, Sr., and also had close friendships with John Dewey and Norman Thomas. His support for civil liberties led him to oppose McCarthyism during the Cold War, which led to false accusations that he was a communist. His writings after 1936 are deeply critical of communism.

From 1940 to 1953, he was the executive Director of the Fellowship of Reconciliation, an influential Protestant pacifist organization, where he did antiwar work, advocated nonviolence within the Protestant ecumenical movement, and helped mentor a number of the Future Leaders of the Civil Rights Movement, including Bayard Rustin. Rustin, a close advisor of Martin Luther King Jr., later claimed that while an advisor to King, he never made a difficult decision without talking about it with Muste first.

In 1951, in order to protest the Cold War, he and 48 others filed Thoreau's essay On the Duty of Civil Disobedience instead of their 1040 Forms.

In 1956, he and David Dellinger founded Liberation, as a forum for the pacifist and anti-war left.

In 1957, Muste headed a delegation of pacifist and democratic observers to the 16th National Convention of the Communist Party. He was also on the national committee of the War Resisters League (WRL) and received their Peace Award in 1958. Always a creative Activist, he led public opposition with Dorothy Day to civil defense activities in New York City during the 1950s and 1960s.

In 1966, Muste traveled with members of the Committee for Non-Violent Action to Saigon and Hanoi. He was arrested and deported from South Vietnam, but received a warm welcome in North Vietnam from Ho Chi Minh.

A.J. Muste died February 11, 1967, at the age of 82. He was remembered by his contemporary, Norman Thomas, as a man who made "remarkable effort to show that pacifism was by no means passivism and that there could be such a thing as a non-violent social revolution."

At the end of his life, Muste took a leadership role in the movement against the Vietnam War. According to legend, Muste stood outside the White House every night during the Vietnam War, holding a candle, regardless of whether it was raining or not. In fact he worked many a day and night during the last two years of his life building a coalition of anti-war groups – including the Spring Mobilization Committee to End the War in Vietnam – that organized massive protests against the war.

The A.J. Muste Memorial Institute was located at the "Peace Pentagon" in New York City, NY, until it was sold in 2016 because of needed expensive structural repairs. The Institute provides office space for various Activist groups, which will now all reside at the new location at 168 Canal Street in Chinatown. Tenant organizations include the War Resisters League and Socialist Party USA.