US President Donald Trump, Canadian Prime Minister Justin Trudeau, and Mexican President Enrique Pena Nieto have signed the deal that will replace the North American Free Trade Agreement (NAFTA).
The revised deal has been renamed as the United States-Mexico-Canada Agreement, or USMCA.
Mr Trump made revising the deal a key part of his 2016 White House campaign, stating that the update would "change the trade landscape forever".
USMCA will govern more than $1tn worth of trade between the countries.
The deal comes after more than a year of negotiations between the countries, with agreement on new car and dairy industry regulations proving particularly challenging.
Mr Pena Nieto hailed it as a "win-win-win”, and Mr Trudeau, while less enthused, said that the USMCA would, at least, resolve the threat of "serious economic uncertainty" that "would have gotten more damaging".
Politicians from each country will still need to ratify the USMCA before it can take effect.