He is the founder of Freedom to Marry, a group favoring same-sex marriage in the United States, serving as president until its 2015 victory and subsequent wind-down.

[1] Wolfson authored the book Why Marriage Matters: America, Equality, and Gay People's Right to Marry, which Time Out New York magazine called, "Perhaps the most important gay-marriage primer ever written".

[10][11] While in law school, Wolfson was a teaching-fellow in political philosophy at Harvard College before he returned to his birthplace as Kings County (Brooklyn) assistant district attorney, prosecuting sex crimes and homicides, as well as serving in the Appeals Bureau.

There, he wrote a Supreme Court amicus brief that helped win a nationwide ban on race discrimination in jury selection (Batson v. Kentucky).

Wolfson and Foley then conducted a trial before Hawaii judge Kevin Chang, which on December 3, 1996, resulted in the world's first-ever ruling in favor of the freedom to marry.

"[14] On April 30, 2001, Wolfson left Lambda to form Freedom to Marry, having secured a "very generous" grant from the Evelyn and Walter Haas Jr.

Following the losses, Wolfson helped organize more than a dozen LGBTQ leaders to recommit to the fight, rearticulate the strategy, and renew the call for an expanded national campaign.

The outcome of many discussions was a concept paper, drafted chiefly by the ACLU's Matt Coles together with Wolfson, "Winning Marriage: What We Need to Do".

After the passage of Proposition 8 in California, Wolfson worked with funders and movement partners to increase capacity for Freedom to Marry as the central campaign to drive the national strategy and create the climate in which litigation could succeed, bringing on National Campaign Director Marc Solomon, messaging expert Thalia Zepatos, digital experts like Michael Crawford, Cameron Tolle, and Adam Polaski, and opening a federal office in Washington, D.C.

Several of these cases reached the U.S. Supreme Court, which ruled on June 26, 2015, in Obergefell v. Hodges that same-sex couples nationwide have the right to marry.

[25] Richard Kim, signatory and founding board member of Queers for Economic Justice, disputes Wolfson's assertion that the same-sex movement is not pushing for a traditional, heterosexual model for all gays and lesbians and creating a political schism, and as such, gravely misrepresent the consequences of their own work for the past 20 years.

"[27] In a New York Times review of Why Marriage Matters, author William Saletan states what he sees as flaws in Wolfson's reasoning.

Wolfson does not favor the civil union or domestic partnership approaches, because semantic differences create "a stigma of exclusion" and deny gay couples "social and other advantages".

[28] After the closure of the organization, Wolfson devoted his time to advising and assisting other movements and social causes in the United States and around the world, sharing the model and lessons learned from the Freedom to Marry campaign.

[32] In 2025, Evan was awarded the Presidential Citizens Medal, one of the highest civilian honors in the United States, by President Joe Biden, alongside 19 others, including Mary Bonauto, who also played key leadership roles in winning marriage equality for same-sex couples.