Drivers will now be able to drive on the new road layout between Kincraig and Dalraddy which stretches around 4km of newly constructed carriageway.
Following the completion of the first part of the road, other parts of the road will now be upgraded.
Keith Brown, cabinet secretary for economy, jobs & fair work, said: “As one of Scotland’s largest and most challenging infrastructure projects, I welcome this important milestone in our A9 dualling programme, with the first stretch of new road in the programme between Kincraig and Dalraddy now in use.
“Along with the ongoing construction work, we are also continuing to progress the design of the other sections to be dualled with three ground investigation contracts awarded in the last few months. These important investigations are helping to inform and shape the design as we work towards identifying preferred routes for a number of sections to be dualled.
“I am also pleased with the strong links the contractor has forged within the community in delivering improvements for the local primary school, assistance with community events, and an innovative association with the Highland Wildlife Park.