Bronfman had two older sisters: Architect Phyllis Lambert, and Minda de Gunzburg, who married Baron Alain de Gunzburg (1925-2004), a great grandson of Joseph Günzburg. Bronfman also had a younger brother, Charles Bronfman. The Bronfmans "kept a kosher home, and the children received religious schooling on weekends. But during the week Edgar and his younger brother, Charles, were among a handful of Jews sent to private Anglophone schools, where they attended chapel and ate pork."

After graduating from McGill University with a B.A. degree, in 1951, he joined the family Business, where he worked as an accounting clerk and apprentice taster. In 1953, he took over as head of the Seagram U.S. subsidiary, Joseph E. Seagram & Sons. He increased the range of products sold by the company, improved distribution, and expanded the number of countries in which Seagram's products were sold. In 1966, Cemp Investments, which managed the family's Investments, bought 820,000 shares of MGM and, in 1969, Bronfman took over the chairmanship of MGM, albeit briefly.

Following his father's death, in 1971, Bronfman took over as President, treasurer and Director of Distillers Corporation-Seagram Ltd. His son, Edgar Jr., succeeded him as chief executive officer of the company in 1994.

When former World Jewish Congress President Philip Klutznick stepped down in 1979, Bronfman was asked to take over as acting head of the organization, then was formally elected President by the Seventh Plenary Assembly, in January 1981. Together with his deputy, Israel Singer, Bronfman led the World Jewish Congress in becoming the preeminent international Jewish organization that it is today. Initiatives such as those seeking to help free Soviet Jewry; expose Austrian President Kurt Waldheim's Nazi past; and to help victims of the Holocaust and their heirs to acquire compensation (including by Swiss banks); raised Bronfman's international profile during the 1980s and 1990s.

On June 25, 1982, Bronfman became the first representative of a Jewish organization to speak before the United Nations. Speaking before the Special Session on Disarmament, Bronfman said, "world peace cannot tolerate the denial of the legitimacy of Israel or any other nation-state ... [and the] charge that Zionism is racism is an abomination."

In 1983, Bronfman suggested that "American Jews should abandon their strongest weapon, the Jackson–Vanik amendment, as a sign of goodwill that challenges the Soviets to respond in kind."

After Mikhail Gorbachev's ascension in 1985, Bronfman's New York Times message began to resonate with the public. In early 1985, Bronfman secured an invitation to the Kremlin and on September 8–11, visited Moscow, becoming the first World Jewish Congress President to be formally received in Moscow by Soviet Officials. Carrying a note from Shimon Peres, Bronfman met with Gorbachev, and initiated talks of a Soviet Jewish airlift. It is said that Peres' note called on the Soviet Union to resume diplomatic relations with Israel.

In 1986 Bronfman was honored with the Chevalier de la Légion d'honneur (Legion of Honour), from the Government of France.

On May 5, 1987, Bronfman spoke to the World Jewish Congress saying Waldheim was "part and parcel of the Nazi killing machine". Waldheim subsequently filed a lawsuit against Bronfman, but dropped the suit shortly after due to a lack of evidence in his favor.

A year later, in 1988, Bronfman returned to Moscow to meet with Soviet Foreign Minister Eduard Shevardnadze. This trip resulted in the Soviets promising to legalize the teaching of Hebrew in the Soviet Union and to establish a Jewish cultural center in Moscow. Bronfman said of this visit, "By their actions, they are indicating that they are eager to get the question of Jewish rights and emigration off the bargaining table. And it is actions, rather than simply words, that count."

Bronfman was a philanthropist who gave large amounts of money to Jewish causes, including Hillel: The Foundation for Jewish Campus Life, which he was credited with helping revive together with Hillel President Richard Joel in the 1990s. The Hillel at New York University is called The Edgar M. Bronfman Center for Jewish Student Life, known by students just as "Bronfman". Bronfman established the Bronfman Youth Fellowships in Israel, a leadership program for Jewish youth, and provided the funding for MyJewishLearning.com, a digital media entity that includes Kveller, a popular Jewish parenting site.

According to Joel Bainerman, in 1991 he was appointed to the International Jewish Committee for Inter-religious Consultations to conduct official contacts between the Vatican and the State of Israel.

Bronfman was awarded the Presidential Medal of Freedom by U.S. President Bill Clinton in August 1999 and the Star of People's Friendship by East German leader Erich Honecker in October 1988.

In 2000, he received the Leo Baeck Medal for his humanitarian work promoting tolerance and social justice, and in 2005 received the Hillel Renaissance Award.

Bronfman was accused by another WJC official of "perfidy" when he wrote a letter to President Bush in mid-2003 urging Bush to pressure Israel to curb construction of its controversial West Bank separation barrier, co-signed by former Secretary of State Lawrence Eagleburger. Former Israeli prime minister Shimon Peres said in support of Bronfman, "Clearly, issues that are open for debate in Israel should be open for debate in the Jewish world."

Bronfman stepped down from his post as President on May 7, 2007, amid scandals and turmoil about Israel Singer. Bronfman's leadership is known for transforming the World Jewish Congress into the powerful organization it is today. As President, Bronfman is remembered most for his diplomacy with the Soviet Union in freeing Soviet Jews.

In April 2012, Bronfman joined the Bill & Melinda Gates Foundation Giving Pledge, a long-term charitable initiative that aims to inspire conversations about philanthropy and increase charitable giving in the United States. Bronfman and 12 others joined the 68 billionaires who had already signed the giving pledge.

Following his death in 2013, Jewish news outlets called Bronfman a “prince of his people,” for his unique combination of lineage, intrigue, and devotion to the Jewish people through learning and philanthropy. Through his Jewish philanthropy, Bronfman became known for his unique approach to Jewish life. A proud Jew who publicly stated his disbelief in God, Bronfman developed his own understanding of Judaism, as he learned Jewish texts and traditions both in his personal life and in his work at The Samuel Bronfman Foundation. In an article, Journalist Ami Eden writes about Bronfman, who chose to incorporate meaningful Jewish traditions into his life, all the while continuing to educate himself about the religion until his final days. Bronfman also promoted the idea that Jewish organizations needed to stop using fear as a selling point, but rather encourage ordinary Jews to take a deeper interest in the substantive heritage they have been born to. Specifically, while much of the American Jewish community saw intermarriage as an epidemic to be curbed, Bronfman considered the trend an opportunity for Jews to learn further with their non-Jewish partners.

The following is a video of the memorial Service held for Edgar M. Bronfman on January 28, 2014 at Lincoln Center.