The collision took place about 11.10am on the A72 Peebles-Innerleithen road, almost four miles east of Peebles town centre, near the turn-off for Cardrona.
The two cars involved were a red Vauxhall Meriva and a silver Honda CR-V.
The other men taken to hospital afterwards were aged 71 and 42.
The 87-year-old man was also rushed to hospital, but medics were unable to save his life.
The names of those injured have not yet been released by the police.
Sergeant Neil Inglis, of Police Scotland’s road policing unit at Galashiels, said: “We are keen to speak to anyone who witnessed the collision or who stopped to assist and has yet to come forward.”
Anyone with any information can contact officers on 101.