The incident happened around 8.55pm on Monday, July 2 at Bulletloan, just outside Kelso, and police are appealing for witnesses.
A grey Seat Ibiza car travelling north was involved a collision with a silver Vauxhall Corsa and a black Ford Fiesta, which were travelling south.
The 95-year-old woman, who was a passenger within the Fiesta, sustained serious injuries and was taken to Borders General Hospital where she sadly passed away.
The road was closed in both directions for around seven hours while emergency services attended the scene and carried out a collision investigation.
Anyone with information that can assist with this ongoing investigation is asked to come forward.
Sergeant Neil Inglis from the road policing unit in Galashiels said: “This incident has tragically resulted in one woman sustaining fatal injuries and our thoughts and sympathies are with her family at this time.
“Our inquiries continue to establish the full circumstances surrounding the collision and anyone who was on the road at the time and witnessed what happened, or who saw these vehicles travelling in the area beforehand, is urged to contact police immediately.
“In addition, anyone with any further information relevant to this ongoing investigation should also get in touch.”
Those with information is can contact the Road Policing Unit in Galashiels via 101, quoting incident number 4423 of July 2.