The crash happened north of Kelly Road, which is about 30 kilometres south of Tuggeranong.

NSW Police said the crash involved a truck and a car.

"A male driver in the car died at the scene and a female passenger suffered minor injuries and was taken to a Canberra hospital in a stable condition," they said in a statement.

The man who died at the scene was a 74-year-old from Magenta on the Central Coast of NSW.

The woman who was taken to hospital, is a 72-year-old, also from Magenta.

Investigations were still ongoing on Saturday into the cause of the collision, a NSW Police spokesperson said.

Traffic was blocked on highway shortly after 2pm on Friday, and motorists were advised to avoid the area.

"The driver of the truck was taken to hospital for mandatory testing."

The Monaro Highway was closed in both directions at Williamsdale on Friday night, but reopened to traffic early on Saturday.

"Motorists are to expect major delays and avoid the area," NSW Police said.

There was also a minor collision on the Monaro Highway in the ACT, between Shepard and Tralee Streets in Hume on Friday.

No injuries were reported in the ACT collision, territory police said.

The Monaro Highway, the arterial that links the Snowy Mountains with the Federal Highway and is used by thousands of Tuggeranong residents every day, has been rated Canberra's worst blackspot in three of the past four years.

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