Police were called to the two-vehicle accident on the A698 near Denholm at about 16:15 on Thursday.
The female driver of a Vauxhall Zafira died at the scene. Three boys aged 12, nine and 18 months, who were in the car with her, were taken to hospital.
Their injuries are not thought to be life-threatening. The driver of a Peugeot 207 was also taken to hospital.
Police said the 26-year-old man's injuries were also not life-threatening.
Anyone who witnessed the accident has been asked to contact police.
A 34-year-old woman has been killed in a crash in the Borders in which three young boys and a man were also injured.