The Pioneer Pipeline includes 131 kilometres of operating pipeline in Alberta.
It runs from west of Drayton Valley to west of Edmonton.
TC Energy says it plans to integrate the pipeline into its Nova Gas Transmission Ltd. (NGTL) system.
As part of the deal, TransAlta will enter into long-term delivery transportation agreements with NGTL.
TransAlta owns and operates electrical power generation assets in Canada, the United States and Australia.