Initially set to be a two-year program, this latest commitment will see the GTs compete until the end of the 2019 campaign.
“We wanted to make sure everyone knows that we are committed to sports car racing globally with WEC and IMSA,” said Raj Nair, Ford executive vice president and chief technical officer.
“The stated goal of our Ford GT programme was to win Le Mans, and we’re very proud that we were able to do that in our first year.
“To commit to a full, four-year assault on both the IMSA and WEC championships shows how serious we are about taking Ford GT racing around the world.”
Ford is currently lying third and eighth in the IMSA series, while its WEC squad is leading the GT standings.
Australian Ryan Briscoe and Brit Richard Westbrook scored the first victory for the GT at Laguna Seca in May.
The manufacturer recorded a 1-3-4 GTE class finish at Le Mans last month, with Sébastien Bourdais, Joey Hand and Dirk Müller scoring the victory in #68 Ford GT.
The win arrived 50 years after Ford claimed its maiden outright Le Mans 24 Hours victory, courtesy of Chris Amon and Bruce McLaren.