U.S. Pipeline and Hazardous Materials Safety Administration approved a repair and restart plan on Sunday and the pipeline "returned to service", TC Energy said.
"We will operate the pipeline at a reduced pressure with a gradual increase in the volume of crude oil moving through the system," the company's statement said.
The pipeline line has been restarted nearly two weeks after it leaked an estimated 383,000 gallons of oil in North Dakota.
TC Energy was ordered by PHMSA to keep the pipeline shut down until corrective action was taken, including sending an affected portion of the pipe to an independent laboratory for testing.
TC Energy said that about 285,600 gallons of crude oil has been recovered, but the cause of the leak has not been disclosed.