Owen Bieber, the president of the United Auto Workers who presided over the union’s decline from power during the 1970s and 1980s as it became the target of far-right assaults, died on Sunday. Mr. Bieber had been suffering from leukemia. He was 90.

Mr. Bieber was a key member of the UAW’s leadership for decades, rising through the ranks as a translator for the union and then a clerk before being named secretary-treasurer in the 1940s. He then became president in 1960, as the UAW’s power in the auto industry evaporated, its members left the union and by the early 1980s, Mr. Bieber was often described as the union’s youngest president.

As his tenure began to show signs of waning power, Mr. Bieber began to fund his own fights for labor justice, including civil-rights causes. Those included his efforts to desegregate Hardee’s restaurants and his focus on electoral politics.

“He was a progressive who was involved in the community and civic affairs,” said Steve Kramlich, a former UAW president. “He was involved in his South Toledo neighborhood and was a great figure in the community.”

Mr. Bieber was an advocate for better wages and benefits for UAW members and called for higher living-wage rates for workers and better job security. In particular, he criticized wage freezes, which he described as economically robbing workers of earnings, and encouraged greater unionization. Mr. Bieber also took a hard line with automakers in the U.S. that weren’t meeting wage levels, with a major success at the UAW-led DaimlerChrysler strike of 1984. But as the Volkswagen and General Motors struggles of the past decade demonstrated, there was increasing outsourcing by manufacturers and plants within automakers in the U.S.

He was diagnosed with leukemia in the spring of 2015 and he took on an advocacy role, speaking to students, political leaders and the media about leukemia research.

“Owen was a passionate and caring man who devoted his life to improving the lives of others,” said his son, David Bieber. “His love of others led him to help numerous organizations, including the International Union of Painters and Allied Trades and the National Labor Law Project. In many cases, it was Owen’s suggestion that we choose an issue over our own self-interest.”

Mr. Bieber leaves his wife of 65 years, BettyAnn Bieber; a son, David Bieber; three daughters, Margaret and Gladys Sinegal and Roberta Beauvais, and eight grandchildren. A viewing will be held Tuesday from 5 to 7 p.m. at the Long & Burton Funeral Home, 475 Broadway, Saginaw, Michigan. A service will be held Wednesday from 11:30 a.m. to noon at St. Andrews Church, 490 West Kittenan Road, Saginaw. Interment will follow at Arcadia Cemetery.