Ellie Gordon, 14, and Jasmine Hamilton, 12, left their homes in Jedburgh yesterday, January 18, and have yet to return home.
Police inquiries so far suggest that the two girls are together and travelled to Johnstone by public transport.
They were last seen about 10pm yesterday in Johnstone town centre.
Their current whereabouts are unknown and their friends and family are becoming increasingly concerned for their wellbeing, say police.
Ellie is described as being 5ft 4in tall and of medium build, with green eyes and dirty blonde, wavy hair. She was wearing blue jeans, a pink Adidas hoodie and green Superdry jacket.
Jasmine is described as being 5ft 6in tall and slim, with long dark hair. She was wearing a black jacket with furry hood, pink sweatshirt and black or blue jeans and carrying a handbag.
Inspector Jim Morrison, of Galashiels police station, said: “Ellie and Jasmine have been missing overnight and have travelled some distance. This is completely out of character.
“Family and friends are understandably worried about them.“
Anyone able to help police locate Ellie and Jasmine is asked to call police on 101, quoting incident No 4,616 of January 18.