David Isaac Dobnievski, known to history as David Dubinsky, was born February 22, 1892 in Brest-Litovsk (currently Brest in Belarus), the youngest of five boys and three girls. Dubinsky and his family moved to Łódź, Poland, shortly before he turned three. David's father Bezalel Dobnievski, a religious Jew, owned a bakery, but limited himself to administrative tasks related to the enterprise. David's mother Shaina Wyshengrad died when he was eight, with his father remarrying a year and a half later. David worked from early childhood delivering bread from his father's bakery to local shops, while attending a Hebrew school, where he studied Polish, Russian, and Yiddish. He was later forced to leave a semi-private school he attended to take work in his father's bakery to replace a brother who had left abruptly.

During the Russian Revolution of 1905, David attended a mass meeting which led to his kinship, if not actual membership, with the Bund, a Jewish socialist organization close to the Russian Social Democratic Workers Party. He joined the bakers' union, which was controlled by the Bund, and owing to his superior education and fluency in several languages, was elected assistant secretary within the union by 1906. By age 15, David was a committed socialist.

In 1907, David was arrested for helping to plan a bakers' strike and was held for three days. In January 1908, David was arrested again, this time for attending a union election meeting held without a police permit. Not quite 16, the boy was held for 18 months in jails in Łódź, Warsaw, and Moscow, before being sentenced to exile in Chelyabinsk, Siberia. While en route to his place of exile, he walked out of the camp where the authorities were holding him and, after several months hiding in Chelyabinsk and Białystok, managed to make his way to the United States in 1911 with a ticket sent to him by one of his brothers, who was living in New York City.

Now a member of Local 10 of the ILGWU, Dubinsky joined a group of members who rebelled against the old guard leadership of that union to argue for fairer distribution of job opportunities within the union. Dubinsky was elected to the local's executive board in 1918, became vice-president of it the following year and President in 1921. He was elected to the International's Executive Board as a Vice-President in 1922.

Policing the industry became much harder, however, as Gangsters invaded the garment district. Both the employers and the union had hired Gangsters during the strikes of the 1920s. Some of them, such as Lepke Buchalter remained in the industry as labor racketeers who took over unions for the opportunities for raking off dues and extorting payoffs from employers with the threat of strikes. Some also became garment manufacturers themselves, driving away unions, other than those they controlled, by violence. While Dubinsky himself remained untouched by graft, a number of officers within the union were corrupted.

Shortly after Dubinsky was elected to the International Executive Board Benjamin Schlesinger, the International's President, resigned. Dubinsky campaigned hard for election of Morris Sigman, a former IWW member who took office in 1923. Sigman began to remove Communist Party members from leadership of locals in New York, Chicago, Philadelphia and Boston. Dubinsky supported Sigman's campaign.

Sigman could not, however, regain control of the New York locals, including Dressmakers' Local 22 and Cloak Finishers Local 9, where the Communist Party leadership and their left wing allies, some anarchists and some Socialists, enjoyed strong support of the membership. Dubinsky, by his own account, thought that Sigman was too rash and appears to have urged him to call a truce after the left wing-led unions led a campaign to reject a proposed agreement that Sigman had negotiated with the industry in 1925, bringing more than 30,000 members to a rally at Yankee Stadium to call for a one-day stoppage on August 10, 1925.

As weak as the ILGWU was in the aftermath of the 1926 strike, it was nearly destroyed by the Great Depression. Its dues-paying membership slipped to 25,000 in 1932 as unionized garment shops shut or went nonunion or stopped abiding by their union contracts.

Dubinsky was somewhat disenchanted with Sigman's leadership by this point; while he was a wholehearted supporter of Sigman's attack on the Communist influence within the union, he thought that Sigman was too abrasive, alienating the right wing almost reflexively, given his dislike of "union bureaucrats" gained through his years in the Industrial Workers of the World (IWW). At the 1928 convention of the ILGWU he first proposed that Sigman resign in favor of Schlesinger – a suggestion seen by many as part of a plan by Dubinsky to become the eventual head of the union. Dubinsky denied any personal ambitions and rebuffed a proposal from Abraham Cahan of the Forward to promote him as Sigman's heir apparent.

The union often saw itself, both before and during Dubinsky's years at the head of the union, as the savior of the industry, eliminating the cutthroat competition over wages that had made it unstable while making workers' lives miserable. Dubinsky took pride in negotiating a contract in 1929 that contained no raises, but allowed the union to crack down on subcontractors who "chiseled". Dubinsky even claimed to have once turned down an employer's wage offer in negotiations as too costly to the employers, and therefore harmful to employees. Dubinsky summarized his attitude by saying that "workers need capitalism the way a fish needs water."

The new party was subject to many of the same fissures that divided much of the left in the late 1930s. For a while after the signing of the Molotov-Ribbentrop Pact, Communists within the ALP condemned Roosevelt as a warmonger because of his support for Britain. At one particularly stormy meeting Dubinsky and the other Leaders were only able to hold their vote endorsing Roosevelt after moving from room to room and calling the police to arrest those who had disrupted the meeting.

The union recovered, however, after the election of the Roosevelt and the passage of the National Industrial Recovery Act, which promised to protect workers' right to organize. As in the case in other industries with a history of organizing, that promise alone was enough to bring thousands of workers who had never been union members in the past to the union; when the union called a strike of dressmakers in New York on August 16, 1933 more than 70,000 workers joined in it – twice the number that the union had hoped for. It did not hurt, moreover, that the local leader of the NRA was quoted as saying – without any basis in fact – that President Roosevelt had authorized the strike. The union rebounded to more than 200,000 members by 1934, increasing to roughly 300,000 by the end of the Depression.

As one of the few industrial unions within the AFL, the ILGWU was eager to advance the cause of organizing employees in the steel, automobile and other mass production industries that employed millions of workers, many of them immigrants or children of immigrants, at low wages. The ILGWU was one of the original members of the Committee for Industrial Organization, the group that John L. Lewis of the United Mine Workers formed within the AFL in 1935 to organize industrial workers, and provided key financial support and assistance; Rose Pesotta played a key role in early organizing drives in the rubber and steel industries.

Dubinsky and Sidney Hillman, leader of the Amalgamated Clothing Workers, helped found the American Labor Party (ALP) in 1936. At the time Dubinsky and Hillman were both nominal members of the Socialist Party, although Dubinsky had, by his own admission, allowed his membership to lapse during the factional fighting of the 1920s. The Labor Party served as a halfway house for socialists and other leftists who were willing to vote for liberal Democratic politicians such as Roosevelt or Governor Herbert Lehman of New York, but who were not prepared to join the Democratic Party itself.

Dubinsky had hopes of launching a national liberal party, headed by Wendell Willkie, the Republican candidate for President in 1940 who had soured on the Republican Party after his defeat in the primaries in 1944. He proposed that Willkie begin by running for Mayor of New York City in 1945; Willkie, however, died before the plan could get off the ground.

Dubinsky ultimately left the ALP in 1944 after a dispute with Hillman over whether labor Leaders in New York, such as Mike Quill, who either were members of the Communist Party or were seen as sympathetic to it, should be given any role in the ALP. When Hillman prevailed, Dubinsky and his allies left to form the Liberal Party of New York. The ALP went on to endorse Henry Wallace in the 1948 presidential election, while the ILGWU campaigned energetically for Harry S. Truman, nearly bringing New York State into his column, despite it being the home state of the Republican nominee, Governor Thomas Dewey.

Dubinsky and the ILGWU played an active role in the Liberal Party for most of the 1950s and up until his retirement in 1966. The ILGWU ended its support for the party after Dubinsky left office.

The union continued to expand its membership after World War II, reaching its apex at 500,000 members in 1965, one year after Dubinsky's retirement. Dubinsky's focus on maintaining the stability of the industry and the union's place in it dampened the union's Desire to gain significant wage increases for its members. The union gradually lost its ability to keep sweatshop conditions from returning, even in the former center of its strength in New York. While the union still had one-half million members in the years immediately after Dubinsky's retirement, the forces that brought about the decline and eventual disappearance of the ILGWU thirty years later, when it merged with the Amalgamated Clothing and Textile Workers Union to form the union known as UNITE, were already at work. In his last years, Dubinsky was often accessible to the union's members.

Dubinsky received the Presidential Medal of Freedom on January 20, 1969. He died September 17, 1982 in New York City.

Dubinsky proved to be far more durable than his predecessors. He did not brook dissent within the union and insisted that every employee of the International first submit an undated letter of resignation, to be used should Dubinsky choose to fire him later. He also acquired the power to appoint key officers throughout the union. As he explained his position at one of the union's conventions: "We have a democratic union – but they know who's boss."