The interchange in Manitoba will open to traffic at 2 p.m. ET. The CentrePort Canada Way will provide a four-lane divided expressway linking the inland port to the Perimeter Highway.
Harper was joined by Canadian Heritage Minister Shelly Glover and the president and CEO of CentrePort Canada, Diane Gray.
The prime minister is not expected to visit the Manitoba ridings of Brandon-Souris and Provencher ahead of Monday's byelections.
Harper did, however, send a letter to Brandon-Souris residents asking them to vote for Conservative candidate Larry Mcguire.
Polls show the Liberals are in a tight race for the traditionally Conservative riding.
Harper attended the Winnipeg Jets game on Thursday night.