ACT for the Earth began as the Against Cruise Testing (ACT) coalition, which was formed in 1982 in opposition to the Canadian government's agreement to test US cruise missiles in Canadian territory. On February 12, 1983, just 45 hours after the umbrella weapons testing agreement was announced in Canadian Parliament, ACT networks demonstrated across Canada, with 4,000 participating at ACT's home city of Toronto. On April 23, 1983 ACT organized its first annual nationwide Spring Protest for Peace, with a day of protest against the cruise. 25,000 people marched in Toronto and over 100,000 more in 20 cities across Canada. This was Canada's largest day of protest to date, eventually surpassed by February 15, 2003. Tens of thousands more joined in national protests throughout the rest of 1983. ACT evolves into ACT for Disarmament, which begins to take on a holistic vision for peace and the environment.

On April 28, 1984 ACT's second annual Spring Protest for Peace attracted 10,000 in Toronto. In August, ACT for Disarmament publishes the first issue of "The ACTivist", a monthly newsletter which eventually develops into a newspaper for Peace, Ecology & Human Rights. The newspaper is delivered free of charge to various outlets across Canada by the various ACT chapters. Circulation eventually reaches 10,000 printed copies.

1985-86 ACT engages in continuing protests against the cruise missile testing drawing tens of thousands of people into the streets. In 1986 ACT launches the International Campaign for the Innu and the Earth to support the Innu struggle against NATO's low-level flight-testing in Nitassinan (Labrador).

On September 30, 1988 ACT pickets Israeli Consulate in Toronto as part of the international day of action to demand the release of Mordechai Vanunu, charged with treason for revealing Israel's nuclear arsenal. ACT then launches the Canadian Campaign to Free Mordechai Vanunu. During October-November, 1988, ACT holds election-time rallies and vigils held in support of Innu demands to meet Canadian government ministers.

In 1989, during October 11-14, ACT stages demos, sit-ins and sea actions against the presence of nuclear-capable USS Constellation in Vancouver. On October 23, 1989 ACT co-sponsors the first ever forum on East Timor in Toronto. Members of the ACTivist editorial collective aid in the formation of the East Timor Alert Network (ETAN), and begin publishing regular campaign updates in the newspaper.

On February 17, 1990, ACT's "End the Invasion" march in Toronto is joined by independent peace activists from the East bloc for the first time in Canadian history. April 3-5: Vigil outside Federal Court supports Innu injunction against low-level flying.

In 1991 ACT for Disarmament becomes a cofounder of the Conscientious Objectors’ Registry in response to the Gulf War as part of a joint initiative with Conscience Canada, the Canadian Friends Service Committee and Mennonite Central Committee Canada.

In 1992, ACT for Disarmament and INFACT win victory in boycott of General Electric, when on November 23 the company decides to discontinue its manufacturing of strategic nuclear weapons.

From 1993-95 ACT for Disarmament coordinates Annual International Days of Action for the Innu and the Earth. This expands to an international week of action, from October 12 to 19, in 1996.

In November 1996, The ACTivist launches it's website, www.the-activist.org, evolving into www.activistmagazine.com in 2004.

In 1998, the ACTivist switches from a newspaper for peace, ecology and human rights to a Magazine format to address the challenges of activism.

1999-2002: The ACTivist joins the ranks of the so-called "summit hoppers", a budding social justice movement which aims to challenge "corporate-led globalization". The ACTivist provided an independent voice at the following actions:

• World Trade Organization (WTO), Seattle, Washington (November 1999)
• World Bank, International Monetary Fund (IMF), Washington, DC (April 2000)
• Organization of American States (OAS), Windsor, Ontario, Canada (June 2000)
• Free Trade Area of the Americas (FTAA) Summit, Quebec City, Canada (April 2001)
• G8 Summit, Genoa, Italy (July 2001)
• G8 Summit, Calgary (June 2002)
• G8 Summit, Scotland (July 2005)

2003 - January: The ACTivist Magazine joins the Toronto Coalition to Stop the War. New ACTivist Magazine Editor stages a 13-day Fast for Peace, calling on Toronto City Council and the Canadian Federal Government to oppose the invasion of Iraq. In June, the ACTivist becomes one of the founding member organizations of the Making the Links Coalition, an organization formed to draw attention to the connections between the harmful practices of the World Trade Organization (WTO) and the Free Trade Area of the Americas (FTAA). September 9th: The ACTivist, through the Making the Links Coalition, assists in organizing a historic teach-in on the WTO and FTAA in Toronto, featuring Naomi Klein, the Yes Men and an audiovisual hook-up to activists in Cancun, Mexico, including Maude Barlowe and Vandana Shiva. September 26: The ACTivist holds Justice Ain't Just Us, a benefit concert, featuring David Rovics, in Toronto. October: The ACTivist joins the Campaign to Stop Killer Coke.

In January, 2004, the ACTivist enters its 20th year. In June, 2004 the ACTivist becomes a cofounder of the War Resisters Support Campaign. Leading up to October 14-16 the ACTivist helps organize Media Democracy Day. October 22: The ACTivist Magazine holds its 20th anniversary celebrations during the culmination of Media Democracy Week. Soon after, ACT for Disarmament evolved into ACT for the Earth.