The ACT has set a global benchmark by becoming the highest level of government in the world to endorse a fossil fuel non-proliferation treaty.
The territory's parliament agreed to sign the treaty, following a motion put forward by Greens backbencher Jo Clay.
The treaty, based on the nuclear non-proliferation treaty, calls for an end to new fossil fuel exploration and expansion, the phasing out of existing production and the development of equitable transition plans.
"Fifty years ago we were facing an existential crisis from nuclear weapons," Ms Clay said.
"We understood that and the world came together ... in three years we put together a global treaty to end the proliferation of nuclear weapons.
"We need to do that now for the climate crisis."
Internationally, only six city- and municipal-level governments have endorsed the treaty, including the cities of Los Angeles, Barcelona and Vancouver.
Chief Minister Andrew Barr said he believed the motion reflected ACT government policy.
"This is a good opportunity for the ACT to join an international cause," he said.
"I believe we are well credentialed to do so in light of all the policies and initiatives and achievements that we have in place."
The treaty signature will be largely symbolic, as the ACT does not produce fossil fuels. Ms Clay said the endorsement would hopefully inspire other governments to sign the treaty.
The motion also called on the ACT government to write to the federal government, along with other state and territories to endorse the treaty.
"We are actually calling on the federal government to take the action that we need to take," Ms Clay said.
"We need the federal government to stop all new fossil fuel projects, we need to stop putting taxpayer subsidies into fossil fuel."
