Bentley, the only child of Alvin M. Bentley, Jr., and Helen Webb Bentley, was born in Portland, Maine, only three months before his father died serving in France during World War I. Although fatherless, Bentley was heir to a family fortune, from his grandfather who founded the Owosso Manufacturing Company. He graduated in 1934 from Southern Pines High School in Southern Pines, North Carolina, and in 1936 from Asheville Prep School in Asheville, North Carolina. He received his bachelor's degree in 1940 from the University of Michigan and attended Turner's Diplomatic School, Washington, D.C., to qualify for the U.S. diplomatic service.
From 1961 to 1962, Bentley was a delegate from the 15th Senatorial District to the Michigan State Constitutional Convention, which produced the Michigan state constitution adopted in 1963. In 1962, Bentley again ran for the U.S. House for a one-term, at-large seat created as a result of the 1960 U.S. Census, but he lost in the general election to Democrat Neil Staebler. He continued public service by receiving appointments to education-related positions in the state. Also, after leaving Congress in 1961, he had returned to the University of Michigan as a graduate student in the History department. Alvin M. Bentley served on the Board of Directors for the National Conference on Citizenship in 1960. While continuing to maintain offices in Washington, D.C., Bentley commuted by air to Ann Arbor to attend classes. He received an M.A. degree in 1963. In 1966, while pursuing a doctoral degree, Governor George W. Romney appointed him to the board of regents of the University of Michigan. He died, aged 50, while on vacation in Tucson, Arizona, of an "inflammation affecting the central nervous system". Bentley had been confined at a wheelchair for two years after "corrective surgery" when his condition suddenly worsened. He is interred in Oak Hill Cemetery in Owosso, Michigan.
Philanthropy
In 1961, Bentley established the Alvin M. Bentley Foundation to support educational, scientific, and charitable projects. Through the foundation, Bentley continues to foster academic excellence in the state of Michigan. In 1983, the foundation established the Bentley Scholarships at the University of Michigan for Michigan residents who have demonstrated academic excellence and promise. The foundation also sponsors Operation Bentley, "a week-long intensive academic program held at Albion College for high school juniors who have been selected to participate in a rigorous and rewarding study of local, state, and national politics." In 1967, he contributed money to the University of Michigan to establish an endowed professorship in the Department of History in memory of his parents. In the mid-1960s, Bentley served as chairman of the Michigan Freedom from Hunger Council, a humanitarian organization set up to gather, interpret, and disseminate information about hunger problems in the world, especially in the Western Hemisphere. Bentley also chaired the Michigan branch of the Partners of the Alliance, an organization that had begun nationally in 1964, to act as a channel through which civic clubs, unions, business and professional groups, schools, and individuals could work directly with groups, villages, or areas in Latin America to improve the way of life in that particular area. The objective was not charity, but the promotion of self-help programs. The State of Michigan took British Honduras as its partner. In 1971, his widow, Arvella D. Bentley, gave a generous donation to the University of Michigan's "Michigan Historical Collections", enabling it to construct a new building which was subsequently renamed the Bentley Historical Library.