The collision, which involved a black Suzuki Ignis and a red Vauxhall Grandland, happened on the A7 north of Hawick at around 4.35pm on Sunday.
Police said the driver of the Ignis, a 75-year-old man, was pronounced dead at the scene.
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The 52-year-old driver of the Grandland was taken to Borders General Hospital for treatment where medical staff describe her condition as serious but stable.
Inquiries are ongoing to establish the full circumstances.
Police are appealing for information about the crash which happened near the junction with Drove Road.
Sergeant Jamie Humpage said: “Our thoughts are with the family of the man who died.
“Inquiries are ongoing to establish the full circumstances and we are keen to speak to anyone driving on the road around the time of the crash to get in touch.
“I would also ask anyone driving on this road between Selkirk and Hawick around the time of the crash with dash-cam, to please check their footage and make contact with officers if it holds anything relevant.”
The road was closed for crash investigations following the collision and re-opened at around 12.15am on Monday.
Anyone with information which could help the investigation is asked to call Police Scotland on 101, quoting incident number 1987 of Sunday January 12.